Microsoft's new release of SQL Server 2014 comes pretty close on the heels of the last SQL Server 2012 release. For many organizations, this could be a hurdle to adoption, because upgrading core pieces of an IT infrastructure can be both costly and resource-intensive. However, SQL Server 2014 has several compelling new features that can definitely justify an upgrade. Here are the overview of SQL 2014 features:
1. New In-Memory OLTP Engine
2. Enhanced Windows Server 2012 Integration
3. Improvement in Business Intelligence
4. Office 365 Integration
In today post, I want to examine SQL Server 2014 In-Memory OLTP from different angles: how to start using it, provide directions for migration planning, review closely many of its limitations, SQL 2014 In-Memory OLTP applicability and see where the SQL Server In-Memory OLTP can be an alternative to in-memory dynamic caching, and where it is complimentary.
The question now is what is Memory Online Transaction Processing?
SQL Server 2014’s biggest feature is definitely its In-Memory transaction processing, or in-memory OLTP, which Microsoft claims make database operations much faster. In-memory database technology for SQL Server has long been in the works under the code name “Hekaton”. Hekaton is a database engine component which is optimized for accessing Memory resident tables. This component is great, it is fully integrated into SQL 2014 database engine.
The Function of Memory Online Transaction Processing
Hekaton facilitates creation of Memory resident Tables (i.e. Memory Optimized Tables) and Indexes. Beside that, it also provide the option to compile the Transact-Sql Stored Procedure accessing Memory Optimized Tables to Machine code. With Memory Optimized Tables, it provide better performance as the core engine uses the lock free algorithm which doesn’t require any lock and latches when the Memory optimized tables are referenced during the transaction processing.
Low Cost Using In Memory OLTP
Sql Server database engine was designed in the days when Main Memory was very costly. As per this design data is stored on the disk and is loaded to the main memory as required for the transaction processing and any changes to the In-Memory data is written back to the disk. This disk IO is main bottle neck for the OLTP applications having huge number of concurrent users, as it involves waiting for locks to be released, latches to be available, waiting for the log writes to complete.
As per the current trend Main Memory prices are less expensive and enterprises can easily afford to have production database servers with Main Memory sizes in TB’s. And this declining Memory prices made Microsoft to re-think on the initial database engine which is designed in the days when Main Memory was costly. And the result of this re-think is the In-Memory OLTP (a.k.a. Hekaton) Database engine component which supports memory resident Tables and Index. In-Memory OLTP engine uses the lock free algorithm (i.e. MultiVersion Optimistic Concurrency Control) which doesn’t require any lock and latches when the Memory optimized tables are referenced during the transaction processing. And for supporting data durability it still writes to the transaction log but the amount of data which is written to the log is reduced considerably.
Migrating to SQL Server 2014 In-Memory OLTP
Migration to In-Memory OLTP has to be performed in a development environment and carefully tested. Your High-Availability design, Databases design, Tables schemas and data, stored procedures, business logic in the database and even application code – all may require many syntax changes to use In-Memory OLTP.
This is not a “click and migrate” process. It requires development cycles, application and database design and code changes.
The right way to use the In-Memory OLTP engine is:
- Plan your production database architecture. The In-Memory OLTP is very different and has many limitations in terms of H/A, Mirroring, Replications available functionalities;
- Plan carefully your new database (and possibly application) design;
- Migrate several specific tables and procedures that are good benefit candidates;
- Develop or change your business-logic to fit the new design;
- Test and evaluate;
To evaluate whether the In-Memory OLTP can improve your database performance, you can use Microsoft new AMR tool (Analysis, Migrate and Report). For helping with actual migration you can use the Memory Optimization Advisor for tables and the Native Compilation Advisor to help porting a stored procedure to a natively compiled stored procedure.
The AMR tool helps identifying the tables and stored procedures that would benefit by moving them into memory and also help performing the actual migration of those database objects. The AMR tool is installed when you select the “Complete” option of “Management Tools”, and is later accessed through SQL Server Management Studio (SSMS) in Reports –>> Management Data Warehouse Transaction performance reports tool:
The AMR tool provides reports which tables and procedures can benefit the most from In-Memory OLTP and provide a hint how complex will be the conversion. The reports show either recommendations based on usage, contention and performance. Here is (graphics may change in the GA release):
After you identify a table that you would like to port to use In-Memory OLTP, you can use the Memory-Optimization Advisor to help you migrate the disk-based database table to In-Memory OLTP. In SSMS Object Explorer, right click the table you want to convert, and select Memory-Optimization Advisor.
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