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Use In-Memory OLTP in Azure SQL Database to improve your application performance

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Applies to: Azure SQL Database

In-Memory OLTP can be used to improve the performance of transaction processing, data ingestion, and transient data scenarios, without increasing the service objective of the database or elastic pool.

Follow these steps to start using In-Memory OLTP in your existing databases.

Step 1: Ensure you are using a Premium or Business Critical tier database

In-Memory OLTP is supported if the result from the following query is 1 (not 0):

SELECT DATABASEPROPERTYEX(DB_NAME(), 'IsXTPSupported');

XTP stands for Extreme Transaction Processing, which is an informal name of the In-Memory OLTP feature.

Step 2: Identify objects to migrate to In-Memory OLTP

SQL Server Management Studio (SSMS) includes a Transaction Performance Analysis Overview report that you can run against a database with an active workload. The report identifies tables and stored procedures that are candidates for migration to In-Memory OLTP.

To generate the report in SSMS:

  • In the Object Explorer, right-click your database node.
  • Select Reports > Standard Reports > Transaction Performance Analysis Overview.

For more information on assessing the benefits of In-Memory OLTP, see Determining if a table or stored procedure should be ported to In-Memory OLTP.

Step 3: Create a comparable test database

Suppose the report indicates your database has a table that would benefit from being converted to a memory-optimized table. We recommend that you first test to confirm the indication by testing.

You need a test copy of your production database. The test database should be at the same service tier level as your production database.

To ease testing, tweak your test database as follows:

  1. Connect to the test database by using SQL Server Management Studio (SSMS).

  2. To avoid needing the WITH (SNAPSHOT) option in queries, set the current database's MEMORY_OPTIMIZED_ELEVATE_TO_SNAPSHOT option, as shown in the following T-SQL statement:

    ALTER DATABASE CURRENT SET MEMORY_OPTIMIZED_ELEVATE_TO_SNAPSHOT = ON;

Step 4: Migrate tables

You must create and populate a memory-optimized copy of the table you want to test. You can create it by using either:

Memory Optimization Wizard in SSMS

To use this migration option:

  1. Connect to the test database with SSMS.

  2. In the Object Explorer, right-click on the table, and then select Memory Optimization Advisor.

    The Table Memory Optimizer Advisor wizard is displayed.

  3. In the wizard, select Migration validation (or the Next button) to see if the table has any features that are unsupported in memory-optimized tables. For more information, see:

  4. If the table has no unsupported features, the advisor can perform the actual schema and data migration for you.

Manual T-SQL

To use this migration option:

  1. Connect to your test database by using SSMS.
  2. Obtain the complete T-SQL script for your table and its constraints and indexes.
    • In SSMS, right-click your table node.
    • Select Script Table As > CREATE To > New Query Window.
  3. In the script window, add WITH (MEMORY_OPTIMIZED = ON) to the CREATE TABLE statement. For more information, see Syntax for memory optimized tables.
  4. If there is a CLUSTERED index, change it to NONCLUSTERED.
  5. Rename the existing table by using sp_rename.
  6. Create the new memory-optimized copy of the table by running your edited CREATE TABLE script.
  7. Copy the data to your memory-optimized table by using INSERT...SELECT * INTO: 
    INSERT INTO [<new_memory_optimized_table>]
SELECT * FROM [<old_disk_based_table>];

Step 5 (optional): Migrate stored procedures

In-Memory OLTP also supports natively compiled stored procedures, which can improve T-SQL performance.

Considerations with natively compiled stored procedures

A natively compiled stored procedure must have the following options in its T-SQL WITH clause:

  • NATIVE_COMPILATION: meaning the Transact-SQL statements in the procedure are all compiled to native code for efficient execution.
  • SCHEMABINDING: meaning that the tables referenced in the stored procedure cannot have their definitions changed in any way that would affect the stored procedure, unless you drop the stored procedure.

A natively compiled module must use one ATOMIC block for transaction management. There is no use of explicit BEGIN TRANSACTION or ROLLBACK TRANSACTION statements. Your code can terminate the atomic block with a THROW statement, for example if it detects a business rule violation.

An example of a natively compiled stored procedure

The T-SQL to create a natively compiled stored procedure is similar to the following template:

CREATE PROCEDURE schemaname.procedurename
    @param1 type1, ...
    WITH NATIVE_COMPILATION, SCHEMABINDING
    AS
        BEGIN ATOMIC WITH
            (
            TRANSACTION ISOLATION LEVEL = SNAPSHOT,
            LANGUAGE = N'<desired sys.syslanuages.sysname value>'
            )
        ...
        END;
  • For the TRANSACTION_ISOLATION_LEVEL, SNAPSHOT is the most common value for the natively compiled stored procedures. However, a subset of the other values is also supported:
    • REPEATABLE READ
    • SERIALIZABLE
  • The LANGUAGE value must be present in the sys.syslanguages view, in the name column. For example, N'us_english'.

How to migrate a stored procedure to use native compilation

The migration steps are:

  1. Obtain the CREATE PROCEDURE script to the regular (interpreted) stored procedure.
  2. Rewrite its header to match the previous template.
  3. Determine whether the stored procedure T-SQL code uses any features that are not supported for natively compiled stored procedures. Implement workarounds if necessary. For more information, see Migration issues for natively compiled stored procedures.
  4. Rename the old stored procedure by using sp_rename, or drop it.
  5. Execute your edited CREATE PROCEDURE T-SQL script.

Step 6: Run your workload in test

Run a workload in your test database that is similar to the workload that runs in your production database. This should reveal the performance gain achieved by the use of In-Memory OLTP for tables and stored procedures.

Major attributes of the workload are:

  • Number of concurrent connections.
  • Read/write ratio.

To tailor and run the test workload, consider using the ostress.exe tool from the RML Utilities group of tools. For more information, see In-memory sample in Azure SQL Database.

To minimize network latency, run ostress.exe in the same Azure region as the database.

Step 7: Post-implementation monitoring

Consider monitoring the performance effects of your In-Memory OLTP implementation in production:

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