SQL Server Whitepaper TOP NEW FEATURES BY GREG ROBIDOUX

Transcription

1 SQL Server Whitepaper TOP 5 NEW FEATURES OF SQL SERVER 2014 BY GREG ROBIDOUX

2 SQL Server 2014 was released to manufacturing on April 1, 2014 and with this version, as well as past versions, Microsoft has introduced new features for the database engine. In this paper, we will explore the top five database engine enhancements that you can take advantage of, learn about what these new features do, and how they improve the SQL Server platform. As with past versions, SQL Server 2014 offers several flavors. The following is a list of all the editions that are available for SQL Server 2014: Enterprise Business Intelligence Standard Web Developer Express with Advanced Services Express with Tools Express Since there are several editions, not all of the features discussed in this paper are available in every edition. For each item that we explore, we will note the specific versions for which this feature is available if it is not available universally. 1 IN-MEMORY OLTP Out of all of the new features in SQL Server 2014, In-Memory OLTP has gotten the most airplay. This is because it functions in a manner drastically different from preceding technology and, with this new feature, Microsoft has seen significant performance gains it operates at up to 20 times the speed of the current SQL Server database engine. In-Memory OLTP uses lock-free and latch-free mechanisms that eliminate the physical locks and latches that are required to ensure data constancy. Because of this locking redesign (and the ability to store data in memory,) SQL Server is able to achieve these huge performance gains. Although the name implies that everything is done in memory, you have the option to pick certain tables to use with In-Memory OLTP while leaving the rest of your database tables as disk-based tables. You also have ability to write queries that reference both in-memory and disk-based tables, so you don t need to try to fit your entire database in-memory. In-Memory OLTP includes memory-optimized tables, which is an architecture change that allows the storage of the table in memory for fast data access. In addition, you can create natively compiled stored procedures that are used exclusively for memory-optimized tables to also get further performance gains. Unlike the traditional query complier, where the query is parsed and compiled on the first execution, the natively complied stored procedure is compiled and put in memory prior to any user query executions. This compiled version is used for all subsequent executions of this stored procedure.

3 A 2000% improvement would be fantastic for every database application, but here are a few things to keep in mind: This feature is only available for 64-bit Enterprise editions, which eliminates the use of this new feature for a portion of SQL Server installations. All tables in a database are limited to 250 GB memory. This may seem like a sufficient amount of memory, but may be an issue for very large databases. It may not yield a 20X performance improvement. You probably already figured this out. Microsoft literature states the improvement can be anywhere from 5-20 times. There may be cases where you only get marginal improvements, so it is crucial that you set up test servers to test this new feature to see what kind of improvements you get, along with the changes that need to be made to take advantage of In-Memory OLTP. Also, if you are thinking about incurring the extra cost for the Enterprise edition so you can take advantage of In-Memory OLTP, make sure you do thorough planning and testing before implementing in production. Once a memory-optimized table has been created, you cannot alter the table. The only option is to drop and recreate the table. The same holds true for natively compiled stored procedures. The only way to alter is to drop and recreate, which will cause the procedure to not be available until the process is completed. Natively compiled stored procedures can only access memory-optimized tables. You cannot use identity columns for the tables. This shouldn t be a showstopper, but for those of you who love to use identity columns, you need to use an alternative like sequence numbers. You can have a maximum of eight indexes per table. Again, this shouldn t be a showstopper, but rather something to be aware of when designing and building your memory optimized tables. Microsoft has developed a tool called the AMR, which is part of SQL Server Management Studio. This tool will help you see the benefits of moving to memory optimized tables and natively compiled stored procedures prior to doing extensive testing. When memory optimized tables are created, there are two options to determine if the data changes persist after a server crash or restart. This is the DURABILITY option. The option can be SCHEMA_ONLY, which only stores the table schema. On restart, the table is created but no data exists. The other option is SCEHMA_AND_DATA, which preserves the table schema along with any data changes that occur. To create a memory-optimized table and natively complied stored procedure, we have to first make sure the database is setup to allow memory-optimized tables. Here is simple example to create a SQL Server 2014 database that allows memory-optimized data and code to create a memory-optimized table and a natively complied stored procedure. -- create database for memory optimized data CREATE DATABASE TestDB ON PRIMARY (NAME = TestDB_file1, FILENAME = N C:\SQLServer\DATA\TestDB_1.mdf, SIZE = 100MB, FILEGROWTH = 10%), FILEGROUP TestDB_MemoryOptimized_filegroup CONTAINS MEMORY_OPTIMIZED_DATA ( NAME = TestDB_MemoryOptimized, FILENAME = N C:\SQLServer\DATA\TestDB_MemoryOptimized ) LOG ON ( NAME = TestDB_log_file1, FILENAME = N C:\SQLServer\DATA\TestDB_1.ldf, SIZE = 100MB, FILEGROWTH = 10%) -- create memory optimized table CREATE TABLE dbo.person ( PersonID INT IDENTITY(1,1) PRIMARY KEY NONCLUSTERED HASH WITH BUCKET_COUNT=400000), FirstName VARCHAR(50) NOT NULL, LastName VARCHAR(50) NOT NULL, ) WITH (MEMORY_OPTIMIZED=ON, DURABILITY = SCHEMA_AND_DATA)

4 -- insert data into the table INSERT dbo.person VALUES ( George, Washington ) INSERT dbo.person VALUES ( John, Adams ) INSERT dbo.person VALUES ( Mickey, Mouse ) INSERT dbo.person VALUES ( Bill, Gates ) -- retrieve data SELECT * from dbo.person -- create natively compiled stored procedure CREATE PROCEDURE int WITH NATIVE_COMPILATION, SCHEMABINDING, EXECUTE AS OWNER AS BEGIN ATOMIC WITH (TRANSACTION ISOLATION LEVEL = SNAPSHOT, LANGUAGE = N us_english ) END SELECT PersonId, FirstName, LastName FROM dbo.person WHERE PersonId=@PersonId -- execute natively compiled stored procedure EXEC usp_getperson 2 ABOUT THE AUTHOR Greg Robidoux is the President and founder of Edgewood Solutions, a technology services company delivering services and solutions for Microsoft SQL Server. Greg is also a co-founder of MSSQLTips.com an online SQL Server community that assists millions of SQL Server professionals. He has been working with SQL Server since 1999 and has authored numerous articles and delivered several presentations. 2 BUFFER POOL EXTENSION This new feature increases the size of the SQL Server buffer pool by allowing the buffer pool to be extended beyond the amount of physical memory allocated to SQL Server. When you have maximized the physical memory, the buffer pool extension allows you to use solid state drives to increase the size of the buffer pool and get the performance gains that solid state drives offer over traditional disks. The buffer pool allows SQL Server to store data in memory without having to constantly access the physical disks. By having more space through using the buffer pool extension, SQL Server is able to store more data and index pages, therefore reducing I/O bottlenecks that often occur with traditional physical disks. Once the buffer pool is filled and there is a request for new data that does not reside in the buffer pool, SQL Server must remove and free up some of the buffer pool pages to allow the new requested information to be loaded into the buffer pool. The more frequently this occurs, the slower the server s overall performance becomes. When data is updated or inserted, these buffer pool pages also need to be written to disk to ensure data in memory is not lost if there is a system failure. The buffer pool now breaks down data, caching into L1 (which is memory) and L2 (which is the buffer pool extension.) The L2 cache only stores clean pages: data that has already been written to disk. The buffer pool extension should improve performance. Here are a few things to note: This new feature is available for both the Enterprise and Standard editions of SQL Server, but only for 64-bit versions. The buffer pool extension can be created or removed at any time and is automatically removed on server shutdown and recreated when SQL Server starts up. The buffer pool extension can be up to 32 times the value of max_server_memory, but Microsoft recommends a 1:4 or 1:8 ratio of memory to buffer pool size.

5 The extension has to be larger than the max_server_memory allocated to SQL Server. So if you have 16GB allocated to SQL Server, the buffer pool extension has to be larger than 16GB. If you remove the buffer pool extension, it is a good idea to restart the server in order to reallocate memory on the server. When setting the buffer pool extension you are not forced to use an SSD, but using a traditional disk defeats the purpose because you are not getting disk performance gains. There are no coding changes that need to be made to take advantage of this once it has been turned on. If there is a need for more buffer pool space, SQL Server will automatically move pages to the buffer pool extension and. If the data resides in the extension, SQL Server will automatically retrieve the data. This may prove to be a big win for the Standard edition. SQL Server 2014 now supports up to 128GB or memory per instance, so with that change (along with the use of the buffer pool extension) you could imagine some big benefits for larger data intensive systems. SQL Server 2014 Standard edition now supports 128GB of memory up from 64GB in prior versions. Here is sample code to turn on the buffer pool extension and to set maximum memory for the server. Once this is turned on, you simply execute your queries as you would normally. -- check max server memory EXEC sp_configure show advanced options, 1; RECONFIGURE; EXEC sp_configure max server memory (MB) ; -- set max server memory to 20GB EXEC sp_configure max server memory (MB), 20480; RECONFIGURE; -- turn on BPE and set to 80GB ALTER SERVER CONFIGURATION SET BUFFER POOL EXTENSION ON (FILENAME = X:\BufferPoolExtension.BPE, SIZE = 80 GB); -- use this if you wan to turn BPE off ALTER SERVER CONFIGURATION SET BUFFER POOL EXTENSION OFF; 3 BACKUP ENHANCEMENTS Overall, the SQL Server backup process hasn t changed that much, but SQL Server keeps getting new features with each new release. This is true for SQL Server 2014 as well. There are a few new enhancements to backup processing that could be useful for your installation. ENCRYPTED BACKUPS The first of these items is the ability to create encrypted backups. SQL Server has historically offered many features for protecting your database data such as Transparent Data Encryption (TDE,) which is only an Enterprise edition feature, and column-level encryption. This is the first time you have been able to create encrypted backups. SQL Server has offered passwordprotected backups, but this option only puts a password on the file that is used when restoring; it never protected the data. There have also been several third-party backup tools that have the ability to create encrypted backups.

6 Here are some things to note about this feature: This is available in the Enterprise, Business Intelligence and Standard editions. You need to create a database master key, similarly to when setting up transparent data encryption. You need to create a certificate again, similarly to when setting up transparent data encryption. Make sure you backup both your key and certificate. If these are lost, you will not be able to restore your backups. You have the ability to create encrypted backups from SQL Server Management Studio or T-SQL. In the past, not all new backup features were accessible from SSMS. You could only do this using T-SQL. If you restore to the same instance, you will not have any issues as long as the master key and certificate still exist. If you restore to a different instance, you will need to create the same master key and certificate. Here is sample code to create an encrypted backup using T-SQL. You will need to set up a master key and certificate prior to creating the backup. -- create master key USE master; CREATE MASTER KEY ENCRYPTION BY PASSWORD = Q2Fddler%3kd0394 ; -- create certificate USE Master CREATE CERTIFICATE BackupEncryptionCertificate WITH SUBJECT = Backup Encryption Certificate ; -- backup database BACKUP DATABASE TestDB TO DISK = N C:\Program Files\Microsoft SQL Server\MSSQL12.SQL2014\MSSQL\Backup\TestDB.bak WITH FORMAT, INIT, MEDIADESCRIPTION = N TestDB encrypted backup, MEDIANAME = N TestDB, NAME = N TestDB-Full Database Backup, COMPRESSION,ENCRYPTION (ALRITHM = AES_256, SERVER CERTIFICATE = [BackupEncryptionCertificate]); Here is a screenshot from SSMS showing the encryption option. This option is on the Backup Options page. You will need to setup a master key and certificate before you can create an encrypted backup.

7 OTHER BACKUP CHANGES There are a couple of other items to check out with SQL Server 2014 when it comes to backups. The first is the ability to backup to a URL via SQL Server Management Studio. This allows you to backup your database directly to Windows Azure Blob Storage. This can be found on the General page of the backup options when you change the Destination from Disk to URL. You might also notice that the option to backup to Tape has gone away. The other change is the ability to create managed backup policies using Windows Azure. This again allows you to use Windows Azure storage for your backups, but also creates database backup retention policies and the ability to encrypt these cloud based backups. Below is a screenshot from SQL Server Management Studio that shows the options for backing up a database to a URL: 4 CARDINALITY ESTIMATION REDESIGN SQL Server 2014 has changed the way the query optimizer works to improve overall query performance. Microsoft introduced this redesign after collecting and analyzing data over several years to improve overall query performance. This is another one of those features that doesn t require any coding changes; your database queries can take advantage of these redesign immediately. In order for database queries to take advantage of these changes, the database has to be in 120 compatibility mode, which is equivalent to SQL Server This can be done either via T-SQL or through SQL Server Management Studio as shown below. ALTER DATABASE TestDB SET COMPATIBILITY_LEVEL = 120; If you go to the Options page under Database Properties you can change this setting, as is shown below:

8 Here are a few things to keep in mind about this change: This is available in all editions of SQL Server Any database with compatibility level of 120 will use the new cardinality estimator for all queries. There are no coding changes that you need to make to take advantage of these enhancements. If the database has a lower compatibility level, it will not use the new estimator. Most queries should be able to get a performance benefit or remain the same, but there is a chance some queries performance could degrade. There is the ability to turn on the new estimator for certain queries using Trace Flag So, if the database compatibility level is lower than 120, you can use this trace flag to turn on the new estimator for the query. There is also the ability to turn off the new estimator for certain queries using Trace Flag So, if the database compatibility level is 120 and there are issues with certain queries, you can use this trace flag to use the old estimator. If the query uses databases from more than one database, the database that was used to compile the query will determine which version of the cardinality estimator will be used. The Buffer Pool Extension improves performance by extending your SQL Server data cache to fast Solid State Drives. Here is an example to turn off the new estimator for a database that has a 120 compatibility level. SELECT * FROM TestDB.dbo.Person OPTION (QUERYTRACEON 9481); The below screenshot shows that the above query is using the older cardinality estimator (value 70):

9 5 REFERENCES ADDITIONAL ENHANCEMENTS TO SQL SERVER 2014 There are even more new features in SQL Server 2014 and it was hard to just pick one of these items over the others for our final Top 5 item, so here are a few other features that you should be aware of in SQL Server MORE SQL MEMORY - STANDARD EDITION One exciting change that many organizations can take advantage of is the increase in memory from 64GB to 128GB per instance of SQL Server for the Standard edition. This should be a huge help for many database installations. As databases continue to grow, the need to keep more data in memory becomes very important. Often, these enhancements are only made available in the Enterprise edition, so it is nice to see that Microsoft has thrown us a bone for the majority of the installations. Using this along with the buffer pool extension could be a big win for your environment. UPDATEABLE COLUMNSTORE INDEXES - ENTERPRISE EDITION In SQL Server 2012, columnstore indexes were introduced, which allow you to have the index storage based on columns instead of rows. By storing column data closely together, these columnstore indexes were able to significantly improve performance for certain types of data and queries. This feature was primarily introduced to help improve data warehouse queries or very large data queries. However, one of the historical downsides to columnstore indexes was that they were read-only. This meant that that after the index was created, the only way to update the data was to recreate the columnstore index. When creating indexes for a columnstore, you now have the ability to create either clustered or nonclustered indexes. In SQL Server 2012, the only option was nonclustered and these indexes were not updatable. With SQL Server 2014 you now have the ability to create a clustered columnstore index, which is updateable As data changes, the index can be updated without having to completely recreate the clustered columnstore index. ALWAYSON ENHANCEMENTS - ENTERPRISE EDITION A few changes for AlwaysOn Availability Groups include the ability to have up to eight secondary replicas, the ability to add Windows Azure replicas using a wizard, and the use of Clustered Shared Volumes. RESOURCE VERNOR IO CONTROL - ENTERPRISE EDITION The resource governor was introduced in SQL Server It gave you the ability to create resource pools to limit memory and processor usage for certain types of database users. In SQL Server 2014, a new feature has been added that also allows you to control physical I/O as part of the resource pool that is configured. DATABASE COMPATIBILITY LEVELS - ALL EDITIONS SQL Server 2014 installations only support database compatibility levels of 100 and greater. This means that if you have any databases that are using a compatibility level less than SQL Server 2008, you will need to adjust the compatibility level in order for it to function on a SQL Server 2014 instance. Books Online for SQL Server 2014 SQL Server 2014 Tips on MSSQLTips.com

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