Oracle database setup

Transcription

1 Oracle database setup Tuomas Pystynen AtBusiness Communications OUGF syysseminaari 2002 Sivu 1

2 Database size Database size Small (1GB) Fits in memory Medium (10GB) Fits on one disk Large (100 GB) Requires planning Very Large (1TB) Requires a lot of planning OUGF syysseminaari 2002 Sivu 2

3 Database Server CPU Select the fastest CPU with largest L2 cache A CPU is cheap compared to Oracle license for the CPU Minimise the number of CPUs needed to run Oracle Many database operations are CPU bound Large L2 cache and fast bus helps the CPU to run at max speed Oracle kernel is large program and accesses a lot of data New CPUs are very fast compared older CPUs inefficient queries or applications can still waste 100% of available CPU power Application and Web servers usually require much more CPU power than database servers OUGF syysseminaari 2002 Sivu 3

4 Database Server CPU types Intel/AMD Best performance/price ratio Intel Xeon 2.4GHz/400MHZ bus/512k L2 Cache Sun UltraSparc UltraSPARC III Cu 1.2GHz/ 8MB L2 Cache HP PA processor 875MHz/2.25 MB L1 Cache HP Alpha Alpha 21264D 1.25 GHz/16 MB L2 IBM Power4 IBM POWER4 1.3 GHz/1.4 MB L2 Comparing different CPU types is difficult OUGF syysseminaari 2002 Sivu 4

5 Database Server Scalabity SMP machines Oracle can exploit multiple CPUs Can use parallel query and other parallel features Clusters Oracle9i RAC scales much better that Oracle8 OPS No need to partition applications OUGF syysseminaari 2002 Sivu 5

6 Database Server Operating system Windows 2000 Advanced Server Linux RedHat Advanced Server V2.1 Supported by Oracle Sun Solaris HP UX HP/Compaq Tru64 Unix IBM AIX OUGF syysseminaari 2002 Sivu 6

7 Database Server Memory At least 1 GB memory Memory is cheap too Relocate SGA may need to change SGA address to allocate over 2GB Using over 4 GB memory per database instance Oracle9i R2 VLM support for Windows 2000/XP Oracle9i R2 VLM support for Redhat 2.1 Advanced Server Solaris 64-bit HP UX bit HP Tru64 Unix IBM AIX 64-bit OUGF syysseminaari 2002 Sivu 7

8 Disk subsystems Internal disks RAID NAS (Network Attached Storage) NetApp, HP,.. SAN (Storage Area Network) EMC, Veritas, Sun, HP,... OSCP Oracle Storage Compatibility Program OUGF syysseminaari 2002 Sivu 8

9 Disk configuration Mirroring Consider mirroring at least critical database files Online redo logs, system and rollback segments RAID-5 is cheap, but slow for writes IO balancing Number of physical disk drives/controllers Disk striping Put Oracle datafiles on specific disks/volumes Caching Many disk subsystems have caches Write caching can improve LGWR OUGF syysseminaari 2002 Sivu 9

10 Database IO Avoid file system buffering for Oracle files Direct IO is always used on Windows Use direct IO or raw devices on Unix/Linux Especially for online redo logs If file system buffering can not be avoided Make sure file system buffer size equals database block size Create file system for Oracle datafiles Use asyncronous IO If asynchronous IO is not supported Use multiple multiple slave processes (dbwr_io_slaves) Do not put Oracle datafiles on file servers Except certified NAS solutions OUGF syysseminaari 2002 Sivu 10

11 Database block size 8K database block size is a good compromise Very large databases may benefit from 16k or 32k block size Indexes will have fewer levels with large block size Less overhead in data blocks Each database block has few hundred bytes overhead Less row chaining for wide tables File system buffer size should match database block size If direct IO or raw devices are not used May need more memory for Oracle buffer cache When large data block sizes are used Oracle9i supports multiple block sizes Each tablespace can be assigned a block size OUGF syysseminaari 2002 Sivu 11

12 init.ora parameters 1 db_name = test db_domain = tuomas.in.atbusiness.com control_files = c :\oracle\oradata\test\ctl1.ora,d:\oracle\oradata\test\ctl2.ora db_block_size = 8192 db_block_buffers = # 400M shared_pool_size = 64M java_pool_size = 1M OUGF syysseminaari 2002 Sivu 12

13 init.ora parameters 2 processes = 512 transactions_per_rollback_segment = 42 open_cursors = 512 serial_reuse = all sort_area_size = optimizer_mode = choose optimizer_index_caching = 100 optimizer_index_cost_adj = 20 OUGF syysseminaari 2002 Sivu 13

14 Control files Use at least 2 control files on different physical devices Recovery is more difficult if all current control files are lost OUGF syysseminaari 2002 Sivu 14

15 Online redo logs Put online redo log files on mirrored disks Use multiple redo log members if mirroring is not used Losing the current online redo log file means data loss and is difficult to recover from OUGF syysseminaari 2002 Sivu 15

16 Datafiles Auto extensible datafiles make management easier Must still have enough disk space available Not possible on raw devices Avoid large (> 2GB) datafiles Large files can be difficult to move or backup OUGF syysseminaari 2002 Sivu 16

17 System tablespace Ensure that system tablespace is large enough Allocate at least 512MB or use auto extend If system tablespace runs out of space the system will fail Do not create user segments in system tablespace OUGF syysseminaari 2002 Sivu 17

18 Undo tablespace Create a tablespace for rollback segments Create all rollback segments in the tablespace Do not create other segments in the tablespace Allow undo tablespace to autoextend Or create a large enough datafile Avoid costly ORA-1650 errors System Managed Undo feature in Oracle9i Simplifies rollback segment creation and management OUGF syysseminaari 2002 Sivu 18

19 Temporary tablespace Create a temporary tablespace Allocate a large enough datafile or allow it to extend Uniform extent size should be > SORT_AREA_SIZE OUGF syysseminaari 2002 Sivu 19

20 Tablespaces Do not create tables in system or undo tablespace Create tablespace(s) for each application Do not put unrelated segments in same tablespace Tablespace is smallest unit of database backup/recovery OUGF syysseminaari 2002 Sivu 20

21 Locally managed tablepaces Use locally managed tablespaces in Oracle8i Space management operations are much faster No data dictionary searches and updates No congestion on ST enque Use UNIFORM extent size Extent size should be at least 256k Multi-block IO does not cross extent boundary Not a problem to allocate hundreds of extents per segment Improves space reuse Any segment can use any freed extent OUGF syysseminaari 2002 Sivu 21

22 Database creation Use a script to create production database Oracle DBCA does not usually create a good database OUGF syysseminaari 2002 Sivu 22

23 Database creation 1 startup nomount create database controlfile reuse logfile group 1 'd:\oracle\oradata\test\log1.ora' size 16M reuse, group 2 'd:\oracle\oradata\test\log2.ora' size 16M reuse, group 3 'd:\oracle\oradata\test\log3.ora' size 16M reuse, group 4 'd:\oracle\oradata\test\log4.ora' size 16M reuse datafile 'd:\oracle\oradata\test\sys1.ora' size 256M reuse autoextend on next 16M maxsize 1024M maxinstances 1 maxlogfiles 4 maxdatafiles 256 maxloghistory 256 noarchivelog character set WE8ISO8859P1; OUGF syysseminaari 2002 Sivu 23

24 Database creation 2 create tablespace rollback_data datafile 'd:\oracle\oradata\test\rbs1.ora' size 64M reuse autoextend on next 16M maxsize 1024M extent management local uniform size 1M; create public rollback segment rbs1 storage (initial 1M next 1M minextents 4 optimal 4M) tablespace rollback_data; create temporary tablespace temporary_data tempfile 'tmp1.ora' size 16M reuse autoextend on next 16M maxsize 1024M extent management local uniform size 1M; OUGF syysseminaari 2002 Sivu 24

25 Database creation 3 create tablespace user_data datafile 'usr1.ora' size 16M reuse autoextend on next 16M maxsize 1024M extent management local uniform @%ORACLE_HOME%\rdbms\admin\catexp OUGF syysseminaari 2002 Sivu 25

26 Oracle9i spfile Spfile is a server side parameter file which replaces the init.ora file spfile is binary file that can not be edited directly spfile is updated using alter system commands spfile is created using create spfile command create spfile from pfile= inittest.ora ; alter system set shared_pool_size = 96M; select name, value from v$spparameter where name like shared% ; OUGF syysseminaari 2002 Sivu 26

27 Query optimizer Cost-based optimizer usually performs better than the rule-based optimizer CBO has more information available CBO knows more access paths than RBO Sometimes CBO makes bad decisions Use cost-based optimizer for new applications Use CBO also in development and test databases test with large enough database Do not migrate existing applications if they work fine with RBO OUGF syysseminaari 2002 Sivu 27

28 Cost-based optimizer Cost-based optimizer needs statistics Use DBMS_STAT package to compute or estimate statistics Compute statistics after populating the database CBO does a very bad job without statistics Consider updating statistics when database grows Can also cause unpleasant surprises Keep the old statistics just in case OUGF syysseminaari 2002 Sivu 28

29 Compute statistics begin dbms_stats.gather_schema_stats( NULL, method_opt => 'FOR ALL COLUMNS SIZE 1', cascade => FALSE); end; / begin dbms_stats.gather_schema_stats( NULL, method_opt => 'FOR ALL INDEXED COLUMNS SIZE 254', cascade => TRUE); end; / OUGF syysseminaari 2002 Sivu 29

30 Optimizer parameters CBO favors full tablescans and sort-merge joins CBO assumes that indexes and tables are not cached Tell CBO that indexes are 100% cached OPTIMIZER_INDEX_CACHING = 100 Tell CBO that only 20% data blocks are read from disk OPTIMIZER_INDEX_COST_ADJ = 20 CBO has improved over the years Use the latest Oracle version if possible Access paths may change when upgrading to a newer version test carefully OUGF syysseminaari 2002 Sivu 30

31 More reading Using Oracle9i to Simplify Database Creation Oracle Performance Tuning Tips Practical Oracle8i Jonathan Lewis Oracle 24x7 Tips and Techniques Venkat S. Devraj Oracle SQL High-Performance Tuning Guy Harrison OUGF syysseminaari 2002 Sivu 31