1. SQL Server “In-Memory”
Faster Daddy, make it go faster!!!
Presented by Pat Phelan
@YetAnotherSQL on Twitter, or

2. SQL Server “In-Memory” Introduction
This presentation was created for a specific question, at a specific PASS Local Group meeting. I’ve taken the liberty of making it more general purpose in the hope of being able to re-present it later!
The specific question was “How do you use SQL Server In-Memory databases?”
The format for this presentation will be:
Basics – What slows SQL Server down
Details – Why does SQL Server slow down, how to you speed it back up
Questions and Answers

3. Fire: A diversion to make a point
We usually understand and use fire safely
Fire can be a great tool
Fire can help us make great food
Fire can help us stay warm
Risks, benefits, understanding

4. We need to pay attention to fire
Fire can get out of hand
We must pay attention to safety
You must understand your fire
Know what is fuel
Know the oxidizer source(s)
Know the heat

5. If we don’t know what we’re doing
Fighting fire you don’t understand is DANGEROUS!
Using the wrong techniques can cause serious damage.
Fire can get out of control
Fire can hurt us
Fire can ruin dinner!!!

6. SQL Server Speed Issues
Latches
Locks
Blocks
This kind of touches on Deadlocks
I/O

7. SQL Server Speed Issues - Latches
Latches ensure memory consistency
Very short duration
Only held within engine
Latches released before control leaves engine
Each latch only protects one page of RAM
GAM and SGAM latches

8. SQL Server Speed Issues - Locks
Locks ensure logical transaction consistency
Usually user or application defined
Locks can be row, table, or database level
Locks can be held until spid or SQL Server restarts!!!

9. SQL Server Speed Issues - Blocks
One process has a latch or lock that another process needs
Usually fixed by code change (application developer)
Usually fixed by timers
Manually fixed by Administrator “Killing” blocking process

10. SQL Server Deadlocks Process 1 locks object A Process 2 locks object B
Other “stuff” might happen here
Process 2 locks object B
Process 1 attempts to lock object B, causing block
Process 2 attempts to lock object A, causing deadlock
A process (usually A or B) will die

11. SQL Server Speed Issues – I/O
Page (usually extent) I/O
Write
Read
Usually fixed by faster storage media
Hybrid disk
Like memory cache
Front end existing storage with faster storage
Flash disk
RAM disk

12. SQL Server “In-Memory” Tables
Code-named Hekaton
First public discussion at PASS Summit 2012
From the Greek
“Heca-” prefix meaning hundreds
“-ton” suffix meaning engine or tool
Hekaton’s goal is to allow up to 100 times “standard speed”
Compatible applications usually see times improvement with no code changes.

13. SQL Server “In-Memory”
Hekaton: Is it another database engine
I see Hekaton as a separate database engine used by SQL Server
Microsoft considers Hekaton to be part of SQL Server
Microsoft also considers Columnstore to be part of the SQL Data Engine

14. SQL Server “In-Memory” design goals
Completely new design
Bw-Tree
Bw-Trees need an hour on its own!
Optimized for In-Memory use
Writes are buffered to disk to preserve ACID compliance
Latch free design
Minimal or no locking
MVCC (Multi-Version Concurrency Control)
Readers and writers never block each other!
Optimistic concurrency used by the engine

15. “In-Memory” Application Migration
Commercial applications designed for In-Memory
User developed applications designed for In-Memory
Applications using only Microsoft libraries for databases
Applications where you have source code

16. In-Memory” Unsupported DDL
Datetimeoffset
Geography
Geometry
Heirarchyid
Rowversion
XML
SQL_Variant
Any user defined data type

17. “In-Memory” Unsupported DDL
LOBs
Text, BLOB, NTEXT
VARCHAR(max), NVARCHAR(max) supported in SQL 2016 and later
IDENTITY(1, 1) supported, but there are some restrictions
Foreign Keys
Check Constraints
No schema changes
Removing or changing index requires droping tables
Some ALTER TABLE and sp_rename allowed in SQL 2016+, none in 2014

18. “In-Memory” Unsupported DML
Data Compression
Replication is limited
Linked Servers
MERGE FROM (source is supported)
Unsupported Features (may work, but no support)
MS-DTC
PBM (Policy Based Management)
MERGE INTO
Triggers

19. “In-Memory” and “In Cloud”
Azure
memory
Amazon AWS
Google Compute
I can’t find a public web reference, but I know at least one case exists
Private cloud providers

20. SQL Server “In-Memory” databases
SSD offers “in Flash Memory” databases
Pure Storage
SIOS
HPE Nimble (again part of HP)
EMC Xtreme IO
NetApp

21. SQL Server “In-Memory” databases
Actual RAM Disk products
MS-DOS and PC-DOS offered the VDISK.SYS device driver
Imdisk
Open Source, Free
No option to buy support, use at your own risk!
DataRAM
4 GB limit
Personal version is free
Primo RAMDisk is $30 for two licenses (as of )

22. Questions and Answers
The only “dumb” questions are the ones that you don’t ask.
In-Memory brings a whole different paradigm, you need to re-think!

23. SQL Server “In-Memory”
Pat is a Database Architect and Mentor at Involta, LLC.
SQL Saturday Iowa 2018
Iowa City, IA 23 June 2018
Pat Phelan