In-Memory OLTP: Comparison of Features/Limitations between SQL Server 2014 and SQL Server 2016

In earlier articles I talked about the In-Memory OLTP Engine in SQL Server 2014. Even though it is very powerful, it had some limitations (note the past tense of "have" here as I have some good news! :)

For example you couldn't use subqueries in the clauses of a SELECT statement inside a natively-compiled stored procedure, or nested stored procedure calls, etc.

Here's the good news: SQL Server 2016 (currently CTP 2.4) lifted all these limitations and provides far more support for In-Memory OLTP, thus making it much easier to use this cool technology.

The table below summarizes the features/limitations of the in In-Memory OLTP Engine in SQL Server 2014 against SQL Server 2016:

Feature / Limitation SQL Server 2014 SQL Server 2016 CTP2
Maximum memory for memory-optimized tables Recommendation (not hard limit): 256 GB Recommendation (not hard limit): 2TB
Collation support Must use a *_BIN2 collation for:
(i) Character columns used as all or part of an index key.
(ii) All comparisons/sorting between character values in natively-compiled modules.

Must use Latin code pages for char and varchar columns.
All collations are fully supported
Alter memory-optimized tables (after creation) Not Supported Supported
Alter natively-compiled stored procedures Not Supported Supported
Parallel plan for operations accessing memory-optimized tables Not Supported Supported
Transparent Data Encryption (TDE) Not Supported Supported
Use of the below language constructs in natively-compiled stored procedures:
- OR and NOT operators
- Subqueries in all clauses of a SELECT statement
- Nested stored procedure calls
- All built-in math functions
Not Supported Supported
DML triggers in memory-optimized tables Not Supported Supported
(AFTER triggers, natively-compiled)
Multiple Active Result Sets (MARS) Not Supported Supported
Large Objects (LOBs):
- varchar(max)
- nvarchar(max)
Not Supported Supported
Offline Checkpoint Threads 1 Multiple Threads
Natively-compiled, scalar user-defined functions Not Supported Supported
Indexes on NULLable columns Not Supported Supported

As a last note, if you want to easily test the In-Memory OLTP Engine of SQL Server, you can download the special software I developed for this purpose called "In-Memory OLTP Simulator".

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