Update: November 17, 2015
Jos de Bruijn has posted an updated list of In-Memory OLTP changes as of CTP3:
I posted earlier about the changes to Availability Groups in SQL Server 2016, which I learned about at MS Ignite largely from a session by Joey D'Antoni and Denny Cherry. Another great session was from Kevin Farlee and Sunil Agarwal on the changes in store for In-Memory OLTP (the feature formerly known as "Hekaton"). An interesting side note: the video of this session shows a demo where Kevin is running CTP2.0 (build 13.0.200) – though it is probably not the build we'll see publicly this summer.
| Feature/Limit | SQL Server 2014 | SQL Server 2016 |
|---|---|---|
| Maximum size of durable table | 256 GB | 2 TB |
| LOB (varbinary(max), [n]varchar(max)) | Not supported | Supported* |
| Transparent Data Encryption (TDE) | Not supported | Supported |
| Offline Checkpoint Threads | 1 | 1 per container |
| ALTER PROCEDURE / sp_recompile | Not supported | Supported (fully online) |
| Nested native procedure calls | Not supported | Supported |
| Natively-compiled scalar UDFs | Not supported | Supported |
| ALTER TABLE | Not supported (DROP / re-CREATE) |
Partially supported (offline – details below) |
| DML triggers | Not supported | Partially supported (AFTER, natively compiled) |
| Indexes on NULLable columns | Not supported | Supported |
| Non-BIN2 collations in index key columns | Not supported | Supported |
| Non-Latin codepages for [var]char columns | Not supported | Supported |
| Non-BIN2 comparison / sorting in native modules | Not supported | Supported |
| Foreign Keys | Not supported | Supported |
| Check/Unique Constraints | Not supported | Supported |
| Parallelism | Not supported | Supported |
| OUTER JOIN, OR, NOT, UNION [ALL], DISTINCT, EXISTS, IN | Not supported | Supported |
| Multiple Active Result Sets (MARS) (Means better Entity Framework support.) |
Not supported | Supported |
| SSMS Table Designer | Not supported | Supported |
* LOB support will not be available in the CTP shipping this summer.
ALTER TABLE is an offline operation, and will support adding/dropping columns, indexes, and constraints. There will be new syntax extensions to support some of these actions. You can change your bucket count values with a simple rebuild (however note that any rebuild will require 2X memory):
ALTER TABLE dbo.InMemoryTable ALTER INDEX IX_NC_Hash REBUILD WITH (BUCKET_COUNT = 1048576);
In addition to these capacity / feature enhancements, there are also some additional performance enhancements. For example, there will be the ability to add an in-memory, updateable, non-clustered columnstore index over either disk-based or in-memory tables. And they have simplified the way that deleted rows are processed (in 2014, those operations use FileStream; in 2016, they will skip this step). There have also been improvements to the migration advisors and the best practices analyzer – they are now lighter on data gathering and provide more context about migration complexity.
There are still some limitations with some of these changes. TDE, as an example, requires additional steps when upgrading a database. But it's clear that as In-Memory OLTP gets more mature, they are chipping away at many of the biggest roadblocks to adoption.
But wait, there's more! If you want to use In-Memory OLTP in Azure SQL Database, there will be a public preview with full support coming this summer. So you won't need your own physical server with 2 TB of memory to push this feature to its limits. Do not expect any trickling of this feature into Standard Edition, however.
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