ORACLE TO SYBASE ASE MIGRATION GUIDE

Transcription

1 ORACLE TO SYBASE ASE MIGRATION GUIDE

2 Table of Contents 1 Introduction Intended Audience What You Should Already Know About Sybase ASE Oracle systems targeted by this Guide Oracle products vs. Sybase products Oracle / Sybase database versions covered Sybase ASE documents and references How to use this Migration Guide Migration process outline Success factors Not covered by this guide: Project aspects Not covered by this guide: Sybase ASE-specific tuning Pre-migration complexity assessment Oracle checklist: datatypes Oracle checklist: category "Simple Conversion" Oracle checklist: category "Partial Rewrite" Oracle checklist: category "Major Rewrite" Database Schema Migration Obtaining the Oracle schema definition Using existing DDL scripts Reverse-engineering the existing schema Using Sybase PowerDesigner for database schema migration PowerDesigner schema conversion steps Reverse-engineering the Oracle schema without Sybase PowerDesigner Special cases in schema migration Mapping the Oracle schema to Sybase ASE databases Schema-related Oracle-Sybase terminology Mapping Oracle Datatypes to Sybase ASE Chained Oracle data rows Search for Sybase ASE reserved words and keywords in Oracle Choosing a lock scheme for Sybase ASE tables The Oracle DUAL Table Migrating server-level aspects Character set Database server case sensitivity ('sort order') Server configuration parameters Storage Migrating the User Logins User passwords Permissions Data Migration Unload Oracle data into ASCII files; load into ASE with "bcp" utility Loading into ASE with "bcp" Unloading from Oracle: FACT (3rd-party tool) Unloading from Oracle: Roll-your-own PL/SQL utility to export Oracle data Unloading from Oracle: use Oracle SQL Developer Use Sybase's Enterprise Connect Data Access (ECDA) Option for Oracle ECDA Example Use Sybase Replication Server Heterogeneous Edition (RSHE) for Oracle Minimal migration downtime with Replication Initial materialization for the replication setup Other considerations Introduction 2

3 6.4 Use a 3rd-party ETL tool that supports both Oracle and Sybase ASE Oracle datatypes requiring special attention for migration Migrating PL/SQL to Transact-SQL Locations of PL/SQL code rd -party tools for PL/SQL migration to T-SQL Transactions and Locking, Oracle vs. Sybase Oracle MVCC vs. Sybase locking Transaction-related migration issues Using ASE implicit/chained transaction mode Transactional DDL Transaction processing in stored procedures Using ASE explicit/unchained transaction mode Using ASE transactional concurrency enhancements Other transactional aspects Miscellaneous migration aspects Cursors Sequences Error/Exception handling Outer join limitations Migrating JDBC/ODBC/ Applications JDBC Oracle Forms DBA Tasks Cross-Reference Oracle-to-Sybase Migration Cross-Reference Oracle-to-Sybase ASE migration: category "Simple Conversion" Oracle-to-Sybase ASE migration: category "Partial Rewrite" Oracle-to-Sybase ASE migration: category "Major Rewrite" Revision history: Rev.1.0: September 2011: initial version Rev.1.1: November 2011: expanded the topic on case-sensitivity; various other additions Rev.1.2: October 2012: many extensions to chapters 3 & 11; added example of sequence equivalent in ASE : December 2012: replaced PowerDesigner and ECDA examples by pointers to a separate document Sybase, Inc. Sybase, Transact-SQL, Adaptive Server Enterprise and Replication Server are registered trademarks of Sybase, Inc. Other product or brand names may be (registered) trademarks of their respective owners. Introduction 3

4 1 INTRODUCTION This Migration Guide aims to provide guidance and assistance with the migration process from an Oracle database to Sybase ASE (Adaptive Server Enterprise). By "migration" we mean the process of changing a client-server application currently using the Oracle database as its RDBMS, such that it uses the Sybase ASE database instead. This Migration Guide has as its primary focus to migrate functionality from Oracle to Sybase ASE. Performance-related aspects of Sybase ASE are not covered (also see section 2.4). 1.1 Intended Audience This Migration Guide is intended for anyone involved in migrating an Oracle database to Sybase Adaptive Server Enterprise (ASE). 1.2 What You Should Already Know The reader is expected to be familiar with relational database concepts, and with Oracle in particular. In addition, introductory knowledge of the Sybase ASE RDBMS is required. For a database migration to be successful, there should be a detailed understanding of the current Oracle-based system, including its high- and low-level architecture, as well as the interaction between the client application and the Oracle database. 1.3 About Sybase ASE Sybase ASE is the database that powers Wall Street. ASE has been delivering rock-solid reliability and top-level performance for the past 25 years. Sybase ASE has a lower total cost of ownership than Oracle, and delivers better performance on the same hardware. Sybase ASE is ready to be the database in any application that runs on Oracle today. 1.4 Oracle systems targeted by this Guide This Migration Guide can be used for migrations of any type of Oracle-based system. While it does not focus on a specific type of application, workload or system design, the majority of Oracle-based migration candidate systems are expected to be transactional systems. This Migration Guide specifically does not aim at migrating SAP Business Suite installations currently running on Oracle, to run on Sybase ASE instead. Since such migrations are covered by product and service offerings by SAP, interested customers should contact SAP directly. 1.5 Oracle products vs. Sybase products Both Oracle and Sybase provide a range of database-related products. The following list illustrates how the main highlevel Oracle products compared to Sybase products. While this list is deliberately kept brief, it provides some basic guidance on how Oracle and Sybase can be aligned. The focus of this Migration Guide is on migration from Oracle Database Server to Sybase ASE. These are usually expected to be OLTP-oriented systems, though this is not required. Oracle Oracle Database Server Oracle OLAP and DW Oracle RAC Oracle Times Ten Oracle Streams Sybase Sybase ASE (Adaptive Server Enterprise) Sybase IQ Sybase ASE Cluster Edition Sybase ASE In-Memory Database Sybase Replication Server Introduction 4

5 1.6 Oracle / Sybase database versions covered This document pertains to Oracle versions 9i, 10g and 11g. The migration target is assumed to be Sybase ASE version 15.7 (or later). Migration to earlier ASE versions is not recommended and not covered by this Migration Guide. If not otherwise specified all references to "ASE" or "Adaptive Server" are considered references to "Sybase Adaptive Server Enterprise". 1.7 Sybase ASE documents and references For more detailed information about Sybase ASE, see for general documents and whitepapers. See for resources specifically focused at (different types of) migrations. These include the document you are currently reading, as well as Migrating an Oracle Database to SAP Sybase ASE with PowerDesigner and ECDA (A Step-By-Step Practical Guide). For ASE documentation and product manuals, see Specifically, the following ASE documents are relevant: Transact SQL User's Guide Reference Manual System Administration Guide Utility Guide Performance and Tuning Guide In addition, Sybase provides technical training for ASE. For details on courses and availability, see Introduction 5

6 2 HOW TO USE THIS MIGRATION GUIDE The focus of this Migration Guide is on the database-specific technical aspects of an Oracle to Sybase database migration project. In particular, it aims to help identify and assess the complexity of the migration when scoping out a migration project, so as to avoid overlooking or underestimating potentially difficult aspects of the system to be migrated. In addition, it helps establish a migration approach by providing and suggesting technical options for various aspects of the migration process. 2.1 Migration process outline This Migration Guide recommends a phased approach towards migrating from Oracle to Sybase ASE. The following phases can be identified, in order of importance and priority: 1. Before starting the actual migration project, assess the complexity of the migration using the checklist in chapter 3. This activity involves identifying specific Oracle features used in the current system which may not have a direct Sybase equivalent. It is strongly recommended to pay sufficient attention to this activity, as this helps to avoid overlooking or underestimating the most difficult parts of a migration. 2. Migrating the database schema is the necessary first step of an actual migration (described in chapter 4). This Migration Guide recommends using Sybase PowerDesigner to reverse-engineer the Oracle schema and convert it to the Sybase ASE equivalent. 3. Migrating server-level aspects such as users (described in chapter 5). 4. Migrating the data itself (described in chapter 6). The approach chosen to perform the data migration is usually driven by the maximum tolerable downtime allowed for the application. It is recommended to consider using 3 rd -party tools for extracting data from Oracle. If minimal application downtime is crucial, consider Sybase Replication Server to reduce this downtime to minutes rather than hours. 5. Migrating Oracle PL/SQL code to Sybase Transact-SQL (also see chapter 7). This needs to be performed both for SQL located in the database (i.e. stored procedures, triggers, SQL functions) as well as for SQL code in client applications. This step tends to be the most complex part of a migration. To assist with this migration step, chapter 11 contains cross-reference between Oracle features and their Sybase ASE equivalent, in the three categories "Simple conversion possible", "Partial rewrite required" and "Major rewrite required". This cross-reference is an extended version of the Oracle checklist in chapter Migration of vendor-specific infrastructural components, such as JDBC drivers (see section 9.5). 7. Convert the maintenance, administration and monitoring tasks. Since these aspects are highly specific for each database brand, "migration" would be a misnomer. Chapter 10 contains a cross-reference of some common DBA aspects. This is however not sufficient for performing a migration, and specific DBA skills, both for Oracle and Sybase, will be required. 8. The primary focus of this Migration Guide is to help achieve functional equivalence of the Oracle system after being migrated to Sybase ASE. As a next step, Sybase ASE-specific optimization and tuning will likely be required in order to achieve desired performance levels. Sybase ASE-specific tuning is not covered by this Migration Guide; see section Success factors Database migrations can be complex, and costly migration failures need to be avoided. The following success factors apply to any Oracle-to-Sybase database migration project: How to use this Migration Guide 6

7 Domain knowledge of the business application(s), system and environment. It is essential to have a full and complete understanding of all applications that access the Oracle database being migrated. This includes the client applications that connect to the Oracle database directly, but also applications that indirectly access the database, for example through an application server. For all these applications, it needs to be understood which data the application accesses in the database, and how it modifies such data. Any SQL code submitted to the database by the application must be identified, as well as how such SQL code can be changed. Availability of sufficient Oracle expertise to analyze all aspects of the database is an absolute requirement. A key activity is to identify which specific Oracle features are used (as per the checklists in chapter 3), especially those which do not have a direct Sybase equivalent. Full access to all Oracle PL/SQL code being used, both in the database and in all client applications. As a minimum, sufficient understanding of Sybase ASE in order to create a functionally working migrated database system. At a later stage in the migration project, more specialized Sybase expertise will likely be needed for Sybase ASE-specific performance tuning and optimization. Having such expertise available at an early stage may be helpful. A comprehensive testing process and production-like environment for validating the migration approach and the affected software applications against the migrated Sybase database. For best results, it is highly recommended to use a copy of production data (as close as possible) as well as hardware which is similar in size to production. 2.3 Not covered by this guide: Project aspects This Migration Guide does not prescribe or suggest how to organize a migration project in terms of preparation, setting up testing procedures, validating the migrated components, etc. These aspects of a migration project are left to requirements, standards, best practices and preferences of the organization undertaking the emigration effort. Please note that the absence of specific recommendations for testing and validation of migrated components does not mean that such activities should not be performed. On the contrary, these activities are essential, and it is recommended to follow generally accepted best practices with respect to software testing and validation. 2.4 Not covered by this guide: Sybase ASE-specific tuning The primary purpose of this Migration Guide is to assist in creating a functionally equivalent Sybase ASE-based system compared with the original Oracle-based system. The purpose of this Migration Guide is not to provide guidance for arriving at an optimally tuned Sybase ASE system; while Sybase ASE-specific tuning will likely be necessary as part of a migration project, this Migration Guide deliberately makes no attempt to cover such tuning aspects. Since ASE-specific tuning is considered to be mostly unrelated to any Oracle-specific aspects or considerations, the reader is referred to the Sybase ASE documentation for background and recommendations about Sybase ASE tuning., specifically the System Administration Guide and the Performance and Tuning manuals. How to use this Migration Guide 7

8 3 PRE-MIGRATION COMPLEXITY ASSESSMENT For a database migration project, it is crucial to have an accurate assessment of the complexity of the migration ahead of time. Here, "complexity" refers to how Oracle-specific features can be mapped to the feature set of Sybase ASE. Before starting the actual migration effort, the current Oracle system should be closely inspected and a list should be drawn up of all types of Oracle-specific features being used, and how many times these occur. For each feature used, it should be determined in which of the following three categories it falls: Simple conversion possible An Oracle feature or statement can be mapped and converted directly to a (nearly) identical Sybase ASE feature, requiring no syntax changes or only simple, local syntax changes only. Examples: most datatype mappings (Oracle VARCHAR2 Sybase VARCHAR); simple SELECT statements Partial rewrite required An Oracle feature or statement can be mapped to a partly equivalent Sybase ASE feature, requiring potentially significant syntax changes and possibly partial rewriting of algorithms. Example: Oracle sequences Sybase ASE identity columns Major rewrite required An Oracle feature or statement has no directly equivalent Sybase ASE feature, requiring rewriting or redesigning of algorithms or parts of applications. Example: Oracle Flashback; Oracle row-level triggers. Categorizing the Oracle features used by the system being migrated helps to identify the areas where most migration complexity is likely to occur. Before deciding to start the migration project, there should be a clear view of the number of occurrences of the features in the categories "Partial rewrite required" and "Major rewrite required" above, and of the effort to migrate these, especially those in the Major rewrite required" category. To assist with this complexity assessment, below are three checklists, corresponding to the categories above, listing a range of Oracle features. Note that additional Oracle features may occur in your system that are not in these checklists; these should be taken into account just as well. The checklists below list the Oracle features only very briefly. Chapter 11 contains extended versions of these checklists with the corresponding Sybase ASE equivalent for each Oracle feature. 3.1 Oracle checklist: datatypes Verify the datatypes used in the current Oracle application; see section 4.7. Also see: section for considerations that apply when migrating data rows whose length exceed an Oracle disk block; section 6.5 for considerations that apply when migrating particular datatypes. 3.2 Oracle checklist: category "Simple Conversion" #cases found Oracle checklist: category "Simple Conversion" Connecting to an Oracle schema The Oracle SQL*Plus slash character sends preceding PL/SQL text to the Oracle server. Semicolon (as a statement delimiter in PL/SQL) Pre-migration complexity assessment 8

9 #cases found Oracle checklist: category "Simple Conversion" The Oracle DUAL table SET SAVEPOINT savepoint-name Variable/Parameter declarations; naming syntax Assign default value in variable declaration Multiple variable declarations with a single DECLARE keyword Declarations without DECLARE keyword in declaration section of stored procedures/functions Variable assignment Transferring table data into a variable Constants %TYPE denotes the datatype of a column in an existing table Dynamic SQL (Execute-immediate) Loops with LOOP/END LOOP FOR loops CURSOR loops Oracle Outer join syntax SET TRANSACTION READ WRITE ALTER TABLE mytable TRUNCATE PARTITION partition_name CREATE OR REPLACE PROCEDURE (or FUNCTION) ALTER PROCEDURE (or FUNCTION) CREATE PROCEDURE IS Stored procedure execution with named parameters (param => value) Stored procedure execution with positional parameters (:var) Stored procedure execution SQL Function declaration with DETERMINISTIC keyword Execution of a SQL Function DECLARE CURSOR cursor-name IS Oracle cursors Pre-migration complexity assessment 9

10 #cases found Oracle checklist: category "Simple Conversion" Cursor Attribute %ISOPEN Cursor Attributes %FOUND, %NOTFOUND Cursor Attribute %ROWCOUNT AFTER triggers (on statement level) INSTEAD OF triggers (on views) SQL%ROWCOUNT BOOLEAN datatype (for PL/SQL variables only) MERGE statement Partitioned tables with composite partitioning Performance-optimized native PL/SQL datatypes (for PL/SQL variables only) BINARY_INTEGER BINARY_DOUBLE BINARY_FLOAT IF-THEN-ELSE Multiple statements in an IF-THEN-ELSE branch Conditional test based on EXISTS subquery String concatenation operator: userenv('sessionid') MOD(X,Y) CEIL() TRUNC(number) SUBSTR() SUBSTR() function with two parameters LENGTH() CHR() REPLACE() TO_CHAR(expression) TO_CHAR(expression, datepart) Pre-migration complexity assessment 10

11 #cases found Oracle checklist: category "Simple Conversion" TO_CHAR(expression, format-string) TO_NUMBER(expression) Date/time functions and calculations SYSDATE, SYSTIMESTAMP TRUNC(date/time [,unit]) LAST_DAY() NVL() function Inconsistent use of upper/lowercase for identifiers (Oracle is case-insenstive for identifiers) Identifiers that are Sybase ASE reserved words (see section 4.8) INSTR() function with two parameters Derived tables (also known as "inline views") without correlation name ALTER TABLE SPLIT PARTITION ALTER TABLE MERGE PARTITIONS Quoted identifiers. Oracle allows using quoted identifiers by enclosing an identifier in double quotes. Oracle hints Pre-migration complexity assessment 11

12 3.3 Oracle checklist: category "Partial Rewrite" For the Oracle features listed below, migration to partly equivalent Sybase ASE features is possible, although potentially significant syntax changes and possibly partial rewriting of algorithms may be required. #cases found Oracle checklist: category "Partial Rewrite" Database links External tables Sequences Table-valued User-defined SQL Functions Pipelined Table Functions Synonyms Comments on database objects Bitmap indexes Temporary tables IS TABLE OF, AS VARRAY(n)OF Nested tables Object tables %ROWTYPE Define a PL/SQL record type by enumerating the fields with IS RECORD OF or TYPE IS RECORD Non-integer RETURN value in stored procedure User-defined Packages Overloaded stored procedures PL/SQL Exception handling; defining exception handlers SQLCODE, SQLERRM RAISE_APPLICATION_ERROR Column Encryption LOB locators Pre-migration complexity assessment 12

13 #cases found Oracle checklist: category "Partial Rewrite" Data compression Retrieving data to the client in stored procedures using DBMS_OUTPUT package DBMS_*, UTL_* package calls (excl. DBMS_OUTPUT) SDO_* package calls SQL*Loader (sqlldr) Materialized Views Global variables (in a PL/SQL package) INTERSECT construct MINUS construct Specific SQL clauses AS OF AS OF TIMESTAMP CONNECT BY DIMENSION DIMENSION BY EXCLUDE GROUPING SETS INCLUDE MEASURES RETURN ALL ROWS RETURN UPDATED ROWS PARTITION BY REFERENCE SYSTIMESTAMP CROSS CUBE FOR KEEP MAIN MODEL NAV NOCYCLE NOWAIT ON ONLY RULES SAMPLE SEED SKIP IGNORE ITERATE NATURAL NULLS NULLS FIRST NULLS LAST ROLLUP SIBLINGS SINGLE REFERENCE LOCKED START WITH UNIQUE UNPIVOT WAIT INITCAP( string-expression ) INSTR() function with three or four parameters NVL2() function DECODE() function Primary key and foreign key with different datatypes, different precision/scale (for numeric datatypes) or different length (for character datatypes) Cluster (as created with CREATE CLUSTER) Pre-migration complexity assessment 13

14 #cases found Oracle checklist: category "Partial Rewrite" SQL functions where the last statement is not RETURN Derived tables (also known as "inline views") using "with" syntax UNIONs in cursors PRAGMA directives Autonomous transactions ON DELETE CASCADE constraints XMLTYPE (XML data type) XML functions extract(), existsnode(), xmlexists(), etc ROWID ROWNUM Pre-migration complexity assessment 14

15 3.4 Oracle checklist: category "Major Rewrite" For the Oracle features listed below, no direct equivalent is available in Sybase ASE. Consequently, rewriting or redesigning algorithms or parts of applications will be required. #cases found Oracle checklist: category "Major Rewrite" Oracle MVCC (Multi-Version Concurrency Control; "writers don t block readers, readers don't block writers") Relevant aspects: Applications or queries relying on non-blocking MVCC Long-running transactions DDL in transactions SET TRANSACTION READ ONLY SQL*Plus autocommit/commit-on-exit SQL*Plus BEFORE triggers Triggers on row level (BEFORE and AFTER) Multiple triggers for a DML type on a table REF CURSOR Regular Expressions; functions REGEXP_LIKE(), REGEXP_SUBSTR(), REGEXP_REPLACE(), REGEXP_INSTR() Windowing queries (SELECT OVER( ) ) SQL function OUT/IN OUT parameters Non-deterministic SQL Functions (functions whose result may be independent of the function input parameters) SQL Aggregate Functions BFILE datatype Oracle Streams; Oracle Data Guard Oracle RAC for high-availability Pre-migration complexity assessment 15

16 #cases found Oracle checklist: category "Major Rewrite" Oracle Flashback Oracle Snapshot Standby Oracle SQL Plan Management AWR (Automatic Workload Repository) Oracle Advanced Queuing Packages for PL/SQL web access OWA_CUSTOM, OWA_CX, OWA_OPT_LOCK, OWA_SEC, OWA_TEXT, OWA_UTIL Oracle Forms Pre-migration complexity assessment 16

17 4 DATABASE SCHEMA MIGRATION The first step in migrating an Oracle database to Sybase ASE is to migrate the database schema. Here, "database schema" refers to the physical data model. In other words, to the definition of the database structure, specifically of the tables, columns, indexes, views, datatypes, etc., typically expressed in SQL DDL (Data Definition Language), for example as e.g. 'create table' statements. There is some potential for terminology clash around the term "schema": As a generic database concept, "schema" is the definition of the database structure as described above, regardless of which database user owns the object(s). In Oracle, a "schema" is an central concept. It is a collection of database objects (tables, views, stored procedures, triggers, etc) owned by a particular user. A decision will need to be made as to how to map an Oracle schema to an ASE schema; see section 4.5 for details. In Sybase ASE, a "schema" is usually understood to refer to the generic concept of database schema. NB: For completeness, ASE also has a command create schema authorization which creates a number of tables and views plus associated permission settings as a transactional unit. This command is however rarely used in ASE and it is not used or discussed further in this Migration Guide. For clarity, this Migration Guide will use "Oracle schema" when referring to the Oracle-specific interpretation of "schema". In all other cases, "schema" refers to the generic concept of "database schema" as above. Please note: none of the methods describes in this chapter converts Oracle's PL/SQL code into Sybase's Transact- SQL, which is needed when converting stored procedures, triggers and SQL functions. 3 rd -party tools which such capabilities exist; see section 7.2 for more information. 4.1 Obtaining the Oracle schema definition When migrating the database schema from Oracle to ASE, we first need to obtain the Oracle schema, and then convert this to a format and syntax that can be used in Sybase ASE. In principle there are two methods to obtain the Oracle schema: Use existing DDL scripts from which the Oracle schema was created in the past; typically, in well-organized environments, such scripts are kept in a source code repository under version control. Reverse-engineer the Oracle schema from the actual Oracle database Using existing DDL scripts If not using a tool to reverse engineer and migrate the schema, then using existing DDL scripts would be the ideal starting point, since no further work is required to obtain the Oracle schema. However, the question is whether it can be guaranteed that such scripts are up-to-date and identical to the actual Oracle database. It is not uncommon to see that changes to the database schema have been made without updating the DDL scripts in the repository. Clearly, basing oneself on incorrect DDL scripts will cause problems later in the migration process. When existing Oracle DDL scripts are available, the next step is to convert the datatypes to Sybase ASE. Section 4.7 describes the mapping from Oracle datatypes to Sybase ASE. In addition, some aspects of the Oracle schema require special attention; see section Reverse-engineering the existing schema The alternative to using existing scripts is to reverse-engineer the Oracle schema from the actual Oracle database. This is more work, and may require special tools, but it has the advantage that the generated DDL is correct. When existing scripts cannot be used or relied upon, this Migration Guide recommends using Sybase PowerDesigner for reverse-engineering and migrating the database schema. Since PowerDesigner can reverse-engineer all tables, indexes, Database Schema Migration 17

18 etc, and automatically convert the Oracle datatypes into their ASE equivalent, this is the fastest and most efficient schema migration method available. Section 4.2 describes how to use PowerDesigner for this purpose. Section 4.3 describes a possible approach to reverse-engineer the schema without PowerDesigner. 4.2 Using Sybase PowerDesigner for database schema migration Sybase PowerDesigner is arguably the most advanced data modeling tool in the market. It is a stand-alone tool, running on Windows. PowerDesigner supports over 30 database types, including Oracle and Sybase ASE. For more information on PowerDesigner, see With PowerDesigner it is relatively straightforward to reverse-engineer most of the Oracle schema and convert it to Sybase ASE. The central concept used by PowerDesigner is the PowerDesigner Physical Data Model (PDM). This is a database-independent model which can be converted to the SQL DDL dialect of each supported database PowerDesigner schema conversion steps For detailed, step-by-step instructions on how to use PowerDesigner to convert the database schema from Oracle to Sybase ASE, see the document Migrating an Oracle Database to SAP Sybase ASE with PowerDesigner and ECDA (A Step-By- Step Practical Guide) at Once the schema is reverse-engineered, run the completed DDL script in Sybase ASE and check for any errors. Note that some aspects of schema migration cannot be handled by PowerDesigner and will have to be handled differently. These aspects are described in section Reverse-engineering the Oracle schema without Sybase PowerDesigner Without using Sybase PowerDesigner, reverse-engineering the schema can be done in a number of ways: Use the Oracle SQL*Plus DESC command on all database objects, and process the output so that they are valid DDL statements. This is likely to require significant manual script coding. Use the Oracle DBMS_METADATA package to extract DDL for the Oracle objects. This involves SQL statements such as the following (for Oracle table 'MY_TABLE', in schema/user 'SALESAPP'). Note that these are only examples, this is not a complete list of all statement required to perform full reverse-engineering: SELECT DBMS_METADATA.GET_DDL('TABLE', 'MY_TABLE', 'SALESAPP') FROM DUAL; SELECT DBMS_METADATA.GET_DEPENDENT_DDL('INDEX', 'MY_TABLE', 'SALESAPP') FROM DUAL; SELECT DBMS_METADATA.GET_GRANTED_DDL('OBJECT_GRANT', 'SALESAPP') FROM DUAL; Use Oracle SQL Developer (a free Java-based tool, downloadable from oracle.com). This uses the DBMS_METADATA package (see previous bullet). Use TOAD (a low-cost tool, commonly used in many Oracle environments) to extract the object definitions, and then manually convert the Oracle datatypes into their ASE equivalent. This could be cumbersome when large numbers of tables are involved. Once the Oracle schema has been reverse-engineered, the Oracle DDL needs to be converted to Sybase ASE syntax, including conversion from the Oracle datatypes to Sybase ASE datatypes. Section 4.7 describes the mapping from Oracle datatypes to Sybase ASE. In addition, some aspects of the Oracle schema require special attention; see section Special cases in schema migration The following schema aspects require special attention: Database Schema Migration 18

19 Oracle allows more columns per table than Sybase ASE (the limit depends on the ASE server's page size and on the table's lock scheme). If the limit in Sybase ASE is exceeded, an error will be raised when trying to create the table. If this occurs, either the ASE server's page size will need to be increased, or the table needs to be split vertically into multiple tables and all queries referencing the table likely have to be modified accordingly If the length of a column exceeds the maximum allowed length in Sybase ASE (the limit depends on the ASE server's pagesize and on the table's lock scheme), such columns will have to be split into multiple columns and placed in additional tables. All queries referencing the column likely have to be modified accordingly. PowerDesigner converts the Oracle BFILE datatype to the Sybase ASE image datatype. Since BFILE is a datatype used to store a locator (link) to an external binary file stored outside of the database, this is not functionally equivalent so application changes may be required. If a different ASE datatype is required, for example, to hold the name of an externally stored file, change it manually. PowerDesigner 15.x cannot automatically convert the Oracle timestamp datatype to bigdatetime in ASE, so this needs to be done manually. PowerDesigner 16.0 (release expected in August 2011) does not have this limitation and will perform the conversion automatically. PowerDesigner 15.x cannot reverse-engineer Oracle users or security details (permissions). PowerDesigner 16.0 (release expected in August 2011) does not have this limitation and is capable of handling these aspects. Since the SQL reserved words are different between Oracle and Sybase ASE, before attempting a database schema migration, all Oracle objects need to be checked against the Sybase ASE reserved words. Any Oracle identifiers that are also Sybase ASE reserved words, need to be changed first. For a complete list of reserved words in Sybase ASE, see Adaptive Server Enterprise->Reference Manual: Building Blocks->Reserved Words. Also see section 4.8 for queries that can be used to search for the occurrence of keywords in the Oracle database. The mapping of Oracle user-defined datatypes to ASE can be difficult and may require extensive manual intervention. The key to user-defined datatype migration is to fully understand the underlying base datatype. Note that user-defined datatypes can be nested. For Oracle, user-defined datatypes is an add-on option to the database and is not widely used. 4.5 Mapping the Oracle schema to Sybase ASE databases Sybase ASE does not have an identical interpretation of the concept of "schema" as the "Oracle schema". When migrating an Oracle schema to Sybase ASE, there are two basic options to map the Oracle schema to Sybase ASE. For the sake of example, let's assume there are two Oracle users john and bill who own an Oracle schema, and each schema has a table named salesdetails. The options are: Perhaps the most straightforward way to migrate, is to map each Oracle schema to a separate ASE database, where each database is owned ('dbo') by the corresponding user. This would result in two ASE databases named john_db and bill_db (different names may of course be chosen), owned by ASE logins john and bill respectively; each database has table named salesdetails, owned by the dbo database user (the full table name would be dbo.salesdetails). However, this results in as many ASE databases as there are users owning an Oracle schema, of which there might be many. While an ASE server can hold up to databases, it is highly impractical from a DBA perspective to have more than databases. Map all Oracle schemas to a single ASE database with a multi-tenancy model. This means that the ASE database user (which is linked to the ASE server login, which is the equivalent of an Oracle user) is used within the database to identify each object's owner. This will result in a more manageable ASE system since there will be less ASE databases. In this case, the example would result in a single ASE database, let's say sales_db, in which ASE logins john Database Schema Migration 19

20 and bill have been added as database users. Under each user, a salesdetails table is created, which will have the full name john.salesdetails and bill.salesdetails. Either option is possible; technically ASE does not favor one over the other, but the multi-tenancy model fits best with ASE's methods for backup and restore. It should be noted that multi-tenancy models are sometimes incorrectly seen as security weaknesses since it would be easier for user bill to access john's tables, since they are located in the same ASE database. This is however not justified: if standard best practices around ASE security are followed, then security can be fully guaranteed. One consideration around multi-tenancy databases is that a backup of a database contains the data from all users in that database. If this is undesirable, for example because each user wants to have a backup copy of his own database, then the first option above (separate ASE databases for each user) should be followed instead. Lastly, it may also be the case that there is only one Oracle schema. In that case, there is no need to qualify the ASE tables with the owner name since they will all be owned by the dbo user. 4.6 Schema-related Oracle-Sybase terminology Following is the high-level terminology mapping of Oracle concepts to Sybase concepts. This table is not intended to be used for direct migration purposes, but only as high-level terminology guidance. Oracle Database Schema Tablespace Segment Undo/rollback tablespace Online redo logs Sybase ASE Database Server Database and objects owned by the same user. Aspects of ASE database and/or database device and/or segment (system/sysaux tablespacease master database; temporary tablespacease tempdb database; user-defined tablespacedatabase device and/or segment) A database object that has space allocated (table, index, materialized view) Transaction log Transaction log User User, Login (see section 5.5) Role Table Temporary table Role Table Temporary table View Materialized View Cluster Index Index-organized table Column-level check constraint View No direct equivalent No direct equivalent Non-unique index Table with clustered index Column-level check constraint Database Schema Migration 20

21 Oracle Column default Unique key Primary key Foreign key Constraints Collections PL/SQL Procedure PL/SQL Function Triggers Package Sequences Snapshot Database links, External tables Procedure Synonym Sybase ASE Column default Unique key or identity property for a column Primary key Foreign key Constraints In PL/SQL, a collection is an ordered group of elements of the same type, such as VARRAYs or nested tables. Transact-SQL stored procedure T-SQL user-defined SQL function (SQL UDF) Triggers No direct equivalent Partly covered by the identity property for a column or dedicated key value table No direct equivalent Proxy Tables and Remote Servers Stored procedure Similar functionality with views for table and view synonyms. All other synonym references must be replaced with fully qualified object strings (database.owner.object) or proxy tables (for synonyms to remote objects). 4.7 Mapping Oracle Datatypes to Sybase ASE The table below describes how Oracle datatypes can be mapped to Sybase ASE datatypes. In most cases the mapping of datatypes is straightforward. For the Oracle datatypes CHAR, VARCHAR2 and RAW, the ASE server page size determines whether or not the mapping can take place; the technical background is that ASE requires a row, and therefore every column, to fit on an ASE database page. By default, ASE uses a 2KB server page size, but 4KB, 8KB and 16KB are also possible. The maximum allowed column length for a column for each ASE server page size depends on various factors such as whether the column is fixed- or variable length and the ASE table's lock scheme. To display full details, run the command dbcc serverlimits in ASE. Oracle Description Sybase ASE Comments / When to use NUMBER(x) Oracle NUMBER(x) datatypes with 0 decimals can be converted into an equivalent Sybase ASE datatypes. BIGINT length of NUMBER datatype > 10 INTEGER SMALLINT length of NUMBER datatype between 6 and 10 and data values <= 2 billion length of NUMBER datatype is between 4 and 5 and data values <= Database Schema Migration 21

22 Oracle Description Sybase ASE Comments / When to use NUMBER(x,y) FLOAT CHAR(x) VARCHAR2(x) DATE TIMESTAMP [WITH [LOCAL] TIME ZONE] alternatively to the mapping path above, these Sybase ASE datatypes can be used. maximum FLOAT precision in Oracle is approx. 38 maximum CHAR size in Oracle is 2000 bytes maximum VARCHAR2 size in Oracle is 4000 bytes for columns (for PL/SQL variables, the max. size is 32767) date/ time precision in Oracle is up to one second. precision of Oracle s TIMESTAMP is 1/ th of a second TINYINT length of NUMBER datatype between 2 and 3 and data values <= 255 BIT length of NUMBER datatype = 1 NUMERIC(x,y) DECIMAL(x,y) MONEY SMALLMONEY translates the Oracle NUMBER datatype one-to-one. MONEY and SMALLMONEY store monetary data.; 4 digits of precision to the right of the decimal point, and 16 / 6 digits to the left for MONEY / SMALLMONEY respectively. DOUBLE precision of actual values > 15 FLOAT precision of actual values <= 15 CHAR(x) TEXT VARCHAR(x) TEXT DATETIME if ASE page size is 4kb or greater; and if ASE page size is 2kb and x <= 1958 if none of the above conditions apply if ASE page size is 8kb or greater; if ASE page size is 4kb and x <= 3988; if ASE page size is 2kb and x <= 1948 if none of the above conditions apply Sybase ASE s DATETIME has a precision of 1/300 th of a second. BIGDATETIME Sybase ASE s BIGDATETIME has a precision of 1 microsecond. ASE does not support time zones. ROWID a pseudo column in Oracle, does not represent a true datatype NUMERIC IDENTITY Also see ROWID on page 62 CLOB Oracle s max. storage capacity for CLOB is 128TB TEXT Sybase ASE can hold a max. of 2GB per column; IQ can hold up to 2PB NCLOB Oracle s max. storage capacity for NCLOB is 128TB UNITEXT Sybase ASE can hold a max. of 2GB per column; IQ can hold up to 2PB BLOB Oracle s max. storage capacity for BLOB is 128TB IMAGE Sybase ASE can hold a max. of 2GB per column; IQ can hold up to 2PB LONG Oracle s max. storage capacity for LONG is 2GB TEXT RAW(x) the RAW datatype in Oracle has a max precision of 2000 bytes BINARY(x) VARBINARY(x) if ASE page size is 4kb or greater; and if ASE page size is 2kb and x <= 1954 IMAGE if none of the above conditions apply Database Schema Migration 22

23 Oracle Description Sybase ASE Comments / When to use LONG RAW Oracle s max. storage capacity for IMAGE LONG RAW is 2GB CHAR(1) BFILE Chained Oracle data rows if this is a packed bit column maintained by a PL/SQL function set / unset / retrieve / query on them. BFILE stores a locator (link) to a binary file outside of the database BIT no direct equivalent Oracle allows long data rows to exceed the size of a disk block. This is known as 'chained rows'. It is possible that such chained data rows, if they exist in the Oracle database, are too long to be stored in Sybase ASE, which requires that a data rows fits on a data page (which is 2KB, 4KB, 8KB or 16KB; use dbcc serverlimits to find the net max row length allowed in ASE). Also, for tables with more than 255 columns, the rows will always be chained. It is important to identify tables that have chained rows before starting the migration. To find how many chained rows occur in a table, run this Oracle query: SELECT owner, table_name, chain_cnt FROM dba_tables WHERE chain_cnt > 0 If chained rows are found, the Oracle command ANALYZE TABLE table-name LIST CHAINED ROWS INTO chained-row-table can be used to identify the actual chained rows. If chained rows are found, it may be needed to modify the data model to ensure that rows are short enough to fit on an ASE page. 4.8 Search for Sybase ASE reserved words and keywords in Oracle Before you can migrate an Oracle schema or Oracle stored procedure, function or trigger, there needs to be a check for reserved words (keywords) that are already identified as either problematic or non-migratable. Oracle allows SQL keywords to be used as identifiers whereas this is not allowed in ASE. For example, the following is valid PL/SQL: CREATE TABLE case (begin VARCHAR2(100), when INT) The following query finds all object names within the Oracle database that are ASE keywords: select owner, object_name, object_type FROM sys.dba_objects WHERE object_name = UPPER('<ASE-keyword>') The following query scans any PL/SQL object within the Oracle database for certain keywords and returns the name and owner of the object as well as the object type for objects containing ASE keywords. This query retrieves the exact code and line number of the occurrence within a stored procedure, function or trigger. Note that this could potentially return a lot of output since the 'line' column may be long. Also note that these keywords could be part of comments or string constants, in which case they can be ignored: SELECT owner, name, type, line, text FROM sys.dba_source WHERE instr(upper(text), UPPER('<ASE-keyword>')) > 0 The queries above should be run for all Sybase ASE reserved words and keywords. The most practical way of running these queries for all ASE keywords is to insert the ASE keywords in an Oracle table, and then run the above queries as a join with this table. For a complete list of reserved words and keywords in Sybase ASE, see Adaptive Server Enterprise->Reference Manual: Building Blocks->Reserved Words. Reserved words can also be displayed with the following ASE query (but check completeness against the ASE documentation!): Database Schema Migration 23

24 SELECT name FROM master..spt_values WHERE type = 'W' 4.9 Choosing a lock scheme for Sybase ASE tables ASE offers a choice of three lock schemes for each database table: allpages, datapages or datarows. allpages is the oldest lock scheme, as well as the out-of-the-box ASE default. It is slightly more efficient for some types of operations. The datapages, and especially datarows, lock schemes provide fundamentally better concurrency characteristics. The concurrency benefits are likely to be relevant when migrating from Oracle to Sybase ASE due to the difference in transaction handling (as described in chapter 8). It is recommended to configure datapages or datarows as the default lock scheme in Sybase ASE. datapages is more efficient, but datarows provides better concurrency (datarows locking is also known as row-level locking). Changing between datarows and datapages for an existing table is instantaneous. In contrast, large tables with the allpages lock scheme may require long downtimes to if their lock schemes need to be changed to datarows or datapages since this requires a full conversion of the table and all its indexes The Oracle DUAL Table In Oracle, a SELECT statement must always be executed against a table, even when retrieving system information, such as the current date/time. For this purpose, Oracle created the DUAL table. Retrieving the system date via SQL looks like this in Oracle: SELECT sysdate FROM DUAL Sybase ASE supports SELECT statements that do not have a FROM clause. The same query in Sybase ASE would look like this: SELECT getdate() To avoid rewriting existing SELECTs that use the DUAL table, it is possible to create a table named DUAL in ASE, which must always contain one and only row: create table DUAL (dummy_col char(1) unique check (dummy_col='x')) insert DUAL values ('X') go If Sybase ASE is created case-sensitive (see section 5.2), you may need to create additional tables named dual, Dual, etc, depending on how disciplined the Oracle developers were in using a consistent spelling for the DUAL table. Alternatively, consider editing the Oracle PL/SQL source code to use only "DUAL", or to remove all references to DUAL completely. Database Schema Migration 24

25 5 MIGRATING SERVER-LEVEL ASPECTS The architecture of the database server, and the way it is configured and managed, are quite different between Oracle and Sybase ASE. This chapter lists some migration aspects that require attention, but without claim for completeness. The reader is urged to consult the Sybase documentation, specifically the "System Administration Guide", for full details. 5.1 Character set When creating a new Sybase ASE server, the character set to be used by the ASE server must be chosen. It is recommended to use the same character for ASE, as is being used for the Oracle database. While the character set in ASE can be changed at a later point in time, it is strongly recommended to avoid this, and to pick the right character set before migrating any Oracle aspects to ASE. 5.2 Database server case sensitivity ('sort order') A difference between Oracle and Sybase ASE is that Oracle is not case-sensitive, whereas Sybase ASE is case-sensitive by default. ASE can be configured to be case-insensitive, by installing a case-insensitive 'sort order'. Moreover, there is also a difference in the scope of case-insensitivity between Oracle and ASE: In a case-insensitive ASE server, case-insensitivity applies to both identifiers and to data comparisons; SQL keywords are always case-insensitive in ASE. In Oracle, case-insensitivity applies only to identifiers (table names, column names, etc), but, by default, not to data comparisons; it is likely that existing Oracle systems use this default. Note that the above applies only to unquoted identifiers; quoted identifiers are case-sensitive in Oracle, though these are not used often. As a result, the following two queries will retrieve different data in a case-insensitive Oracle system, but retrieve the same data in a case-insensitive Sybase ASE: select * from Employees where Name = 'Johnson' select * from Employees where Name = 'JOHNSON' Also, existing Oracle SQL code refers to the table TEST in different ways - the following all refer to the same table. Inconsistent use of upper- and lower-case spelling for identifiers is not uncommon to occur in practical Oracle systems: select * from TEST select * from Test select * from test When using a case-insensitive sort order for Sybase ASE, such SQL statements do not need to be changed. When using the default case-sensitive ASE sort order, all references to a table must use the exact same upper/lowercase spelling, or "table not found" errors will result. Whether the ASE server should be case-sensitive or case-insensitive is a decision to be made. For ASE, there is no overriding technical advantage to either option. In practice, the decision probably depends on whether query results may be affected by using a case-insensitive ASE server. If this is the case, then the default case-sensitive ASE configuration should be used, and any Oracle SQL statements referring to identifiers in mixed-case spelling (i.e. TEST and Test) should be changed to use one consistent spelling for the identifiers. Migrating server-level aspects 25