Real world SQL 2016 In-Memory OLTP

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1 Real world SQL 2016 In-Memory OLTP Ned Otter SQL Strategist #588

2 About me SQL Server DBA since 1995 MCSE Data Platform Passionate about SQL Server Obsessed with In-Memory

3 KEY TAKEAWAYS ARCHITECTURE RTO RESOURCES

4 Whole database solution

5 Desired workload characteristics Concurrency Write level Latency/contention Hot data Business logic in High Intensive localized Bounded Database

6 Use cases High throughput, low latency

7 Use cases High throughput, low latency Caching/session state

8 Use cases High throughput, low latency Caching/session state Data ingestion (IoT)

9 Use cases High throughput, low latency Caching/session state Data ingestion (IoT) TempDB object replacement

10 Use cases High throughput, low latency Caching/session state Data ingestion (IoT) TempDB object replacement ETL

11 Workload evaluation App suffers from Latency (engine) In-Memory helps because No locks/latches/spinlocks (last page of CI)

12 Workload evaluation App suffers from Latency (engine) In-Memory helps because No locks/latches/spinlocks (last page of CI)

13 Workload evaluation App suffers from High CPU In-Memory helps because Native compilation uses less CPU cycles

14 Workload evaluation App suffers from High CPU In-Memory helps because Native compilation uses less CPU cycles

15 Workload evaluation App suffers from Latency (logging) In-Memory helps because No WAL (no UNDO) More efficient logging Index changes not logged

16 Workload evaluation App suffers from Latency (logging) In-Memory helps because No WAL (no UNDO) More efficient logging Index changes not logged

17 Workload evaluation App suffers from In-Memory helps because Latency (TempDB) In-Mem temp objects don t use TempDB

18 Workload evaluation App suffers from In-Memory helps because Latency (TempDB) In-Mem temp objects don t use TempDB

19 How In-Memory OLTP can help You need better Performance In-Memory helps because Lower CPU (native) Less logging No logging (idx, temp objects) Scalability Latching Locking not possible Spinlock

20 Concurrency model - disk Pessimistic Optional db setting for RCSI/SI (row versions) TempDB Solves R/W blocking W/W still blocks

21 Concurrency model - memory Optimistic MVCC Row versions mandatory for In-Mem workloads Memory Solves R/W and W/W blocking First writer wins, other writers fail (conflict error)

22 Potential workload issues Excessive conflicts Chatty applications/short procs Resource issues: memory/storage/iops

23 New potential bottlenecks WRITELOG IOPS PRIMARY KEY generation

24 Deciphering Editions in SQL 2016/SP1 Max In-Mem/ Edition Enterprise Standard Web Express Columnstore OS limit/os limit 32 GB/32 GB 16 GB/16 GB 352 MB/352 MB

25 Standard Edition (32 GB) Feature Per db Per instance In-Memory Yes No

26 Standard Edition (32 GB) Feature Per db Per instance In-Memory Yes No Columnstore Depends Depends

27 Standard Edition (32 GB) Feature Per db Per instance In-Memory Yes No Columnstore Depends Depends Columnstore/In-Mem tbl Yes No

28 Standard Edition (32 GB) Feature Per db Per instance In-Memory Yes No Columnstore Depends Depends Columnstore/In-Mem tbl Yes No Columnstore/HD tbl No Yes

29 Proof of concept CORES CONCURRENCY COMPLEXITY TOOLS

30 ARCHITECTURE

31 Data/delta files DATABASE NO MAXSIZE FILEGROUP CONTAINER (FOLDER) DATA/DELTA FILES

32 IN-MEMORY DB ARCHITECTURE FILEGROUPS PRIMARY MDF LDF MEMORY-OPTIMIZED Container1 DATA/DELTA Container2 DATA/DELTA

33 001 to to to to to 500 Data/delta files durable data DATA Checkpoint File Pairs DELTA

34 001 to to to to to 500 Garbage Collection File Merge DATA DELTA

35 001 to to to to 500 Garbage Collection File Merge DATA DELTA

36 Data/delta files Shared IFI

37 ROW VERSIONS

38 INDEX Row versions Row = version!!! V1 V2 V3 MEMORY VERSION 1 VERSION 2 VERSION 3

39 Row versions DELETE UPDATE

40 201 to 300 Row versions VERSION 1 begin1 end1 DELETE EXISTING ROW VERSIONS = 1

41 201 to 300 Row versions VERSION 1 begin1 end :56:35 DELETE TOTAL ROW VERSIONS = 1

42 Row versions UPDATE VERSION 1 begin1 end1 EXISTING ROW VERSIONS = 1

43 Row versions UPDATE = VERSION 1 begin1 end1 DELETE + INSERT EXISTING ROW VERSIONS = 1

44 Row versions UPDATE = VERSION 1 DELETE + begin1 end :56:35 INSERT EXISTING ROW VERSIONS = 1

45 Row versions UPDATE = VERSION 1 begin1 end1 DELETE + VERSION :56:35 INSERT begin2 end2 TOTAL ROW VERSIONS = 2

46 Memory dance Buffer pool In-Mem OLTP DEFAULT POOL

47 Memory dance ADD IN-MEM ROWS Buffer pool In-Mem OLTP DEFAULT POOL

48 Memory dance PRESSURE ON BUFFER POOL Buffer pool In-Mem OLTP DEFAULT POOL

49 Memory dance DELETE IN-MEM ROWS Buffer pool In-Mem OLTP DEFAULT POOL

50 Memory dance WANTS TO GROW Buffer pool PRESSURE ON In-Mem In-Mem OLTP DEFAULT POOL

51 Memory dance Buffer pool In-Mem OLTP DEFAULT POOL

52 Row versions VERSION 1 begin1 end1 VERSION 2 begin2 end2 What could possibly go wrong????

53 Buffer Pool Buffer Pool Buffer Pool Buffer Pool

54 COMPRESSION PAGING

55 RESOURCE GOVERNOR Enterprise Resource pool % Initial binding Monitoring

56 Monitoring resource pools Agent Performance Condition Alert (static) SQL Server Event Alert (reactive) sys.dm_os_performance_counters (polling) PoSH Get-WmiObject (dynamic) (PoSH v1) Get-CimInstance (PoSH v3+)

57 GARBAGE COLLECTION

58 Garbage Collection attributes Background Self-throttling Cooperative

59 Garbage Collection process IDENTIFY UNLINK SCHEDULE

60 Garbage Collection: Identify INDEX ROWS IN MEMORY SELECT * FROM table WHERE col = x S C A N V1 V2 V3 VERSION 1 VERSION 2 VERSION 3

61 Garbage Collection: Unlink INDEX ROWS IN MEMORY SELECT * FROM table WHERE col = x S C A N V3 VERSION 1 VERSION 2 VERSION 3

62 Garbage Collection: Schedule SELECT * FROM table WHERE col = x SELECT * FROM table WHERE col = y SCH SCH

63 Garbage Collection verification SELECT current_queue_depth FROM sys.dm_xtp_gc_queue_stats

64 Garbage Collection issues Long/cancelled transactions Table variables DBA cannot control

65 MEMORY

66 Windows Server max memory Windows 2012R2 = 4TB Windows 2016 = 24TB

67 Memory capacity planning Indexes Table variables Row versions Temporal/Staging Sorting (Native) Index/data growth

68 RESTORE

69 RESTORE

70 RESTORE

71 RESTORE FILELISTONLY LogicalName PhysicalName Type FileGroupName Size MyDBData h:\sqldata\mydb.mdf D PRIMARY MyDBlog h:\sqldata\mydb.ldf L NULL MyDBFG1 h:\sqldata\fg1 S FG MyDBFG2 h:\sqldata\fg2 S FG

72 RESTORE PHASES CREATE files (MDF/LDF/DATA/DELTA)

73 RESTORE PHASES CREATE files (MDF/LDF/DATA/DELTA) COPY data from backup file (NORECOVERY)

74 RESTORE PHASES CREATE files (MDF/LDF/DATA/DELTA) COPY data from backup file (NORECOVERY) STREAM data to memory (RECOVERY)

75 Why is the number and placement of containers absolutely critical? CONTAINER (FOLDER) DATA/DELTA FILES

76 Recovery process MEMORY-OPTIMIZED TABLES CONTAINER CREATE files COPY data STREAM data

77 Recovery process MEMORY-OPTIMIZED TABLES CONTAINER 1 CONTAINER 2 CONTAINER 3 CONTAINER 4

78 Recovery events OFFLINE/ONLINE SQL restart RESTORE Server boot READ_ONLY READ_WRITE READ_COMMITTED_SNAPSHOT ON/OFF

79 Potential recovery issues CPU bound FCI/AG (durable) PIECEMEAL

80 CORRUPTION

81 Corruption: Detection and Recovery Method Harddrive Memory CHECKDB YES CHECKTABLE YES Page-level restore (mirroring/ag) YES Recover data from NC indexes YES Hack attach YES RESTORE REBUILD LOG YES

82 Corruption: Detection and Recovery Method Harddrive Memory CHECKDB YES NO* CHECKTABLE YES NO** Page-level restore (mirroring/ag) YES n/a Recover data from NC indexes YES NO Hack attach YES NO RESTORE REBUILD LOG YES NO

83 Corruption: Detection and Recovery BLOCK CHECKSUM

84 Corruption: Detection and Recovery CHECKDB Alternative: BACKUP <db> FILEGROUP = <mem-optimized FG> TO DISK = nul WITH COPY_ONLY

85 CHECKSUM failure Corruption detection point Action Regular processing, i.e. File Merge Sev 21, Error Backup/Restore Sev 16, Error Database recovery (OFFLINE/ONLINE) Sev 21, Error 3414

86 MIGRATING DATA

87 From disk to memory COMPRESSION

88 Considerations for migrating data RECOVERY MODEL TLOG BUCKET COUNT SELECT INTO

89 Migrating data Source Target Same db Disk table Memory table Yes Memory table Disk* Yes Memory table Memory table Yes

90 Migrating data Source Target Same db Cross db Disk table Memory table Yes No* Memory table Disk* Yes No* Memory table Memory table Yes No*

91 Migrating data: cross-database SOURCE DB INSERT to in-mem table variable/ SELECT FROM disk or memory table DESTINATION DB INSERT in-mem table/ SELECT FROM in-mem table variable

92 Migrating data: cross-database SOURCE DB bcp out from disk-table DESTINATION DB bcp into in-mem table

93 Migrating data: cross-database SOURCE DB SELECT INTO ##Table DESTINATION DB INSERT in-mem table EXEC proc (SELECT FROM ##table)

94 Migrating data: cross-database

95 Migrating data: cross-database

96 Benchmark - source table on SSD Sessions Rows in batch Duration Rows inserted minutes 1,248, seconds 5 million seconds 5 million seconds 5 million seconds 10 million seconds 15 million

97 Security ALWAYS ENCRYPTED TDE*

98 Transaction log latency PERSISTENT MEMORY NVDIMM-N TDE

99 ALTER TABLE

100 ALTER TABLE Multi-threaded/logs metadata only OFFLINE SCHEMABINDING Memory requirements

101 ALTER TABLE exceptions Add/alter variable length LOB Add/drop COLUMNSTORE index Column movement: on-row / off-row Create new off-row column

102 Parallelism ALL INDEX TYPES TABLES/VARIABLES SAMPLED STATS DML SOURCE

103 Parallelism NATIVELY COMPILED DML TARGET

104 NATIVE COMPILATION ISSUES

105 Native compilation issues EXEC

106 Native compilation issues Issue Named parameters Mismatched datatypes xevents reason named_parameters parameter_conversion natively_compiled_proc_slow_parameter_passing

107 INDEX ISSUES

108 Index issues Dupes/collisions (100+) Wrong BUCKET_COUNT (HASH) Searching on subset of key columns (HASH) Inequality predicates (HASH) sys.dm_db_xtp_hash_index_stats (avg_chain_length)

109 STATISTICS

110 STATISTICS Manually created Auto created Auto updated (compatibility level) Manually updated (UPDATE STATISTICS) Native modules

111 INDEX MAINTENANCE

112 Index maintenance FRAGMENTATION FILLFACTOR REORGANIZE

113 Index maintenance HASH REBUILD: BUCKETS

114 ZERO FREE SPACE

115 Out of free space MEMORY-OPTIMIZED TABLES 0 FREE NO MAXSIZE C 1/V 1 C 2/V 2 C 3/V 3 TLOG

116 Out of free space MEMORY-OPTIMIZED TABLES 0 FREE NO MAXSIZE C 1/V 1 C 2/V 2 C 3/V 3 TLOG 50 GB FREE C 4/V 4

117 CONTAINER REDISTRIBUTION

118 Container redistribution MEMORY-OPTIMIZED TABLES RTO = 30m C 1/V 1 C 2/V 2 C 3/V 3 NOW: 50GB USED, RESTORE = 15 minutes

119 Container redistribution MEMORY-OPTIMIZED TABLES RTO = 30m C 1/V 1 C 2/V 2 C 3/V 3 LATER: 150GB USED, RESTORE = 45 minutes

120 Container redistribution MEMORY-OPTIMIZED TABLES RTO = 30m C 1/V 1 C 2/V 2 C 3/V 3 C 4/V 4

121 Container redistribution MEMORY-OPTIMIZED TABLES OLD RTO C 1/V 1 C 2/V 2 C 3/V 3 NEW C 4/V 4 C 5/V 5 C 6/V 6 C 7/V 7 C 8/V 8

122 Container redistribution CREATE containers on NEW volumes DROP containers on OLD volumes

123 Best practices, Data Migration Create optimal migration plan Any compression on table(s) to be migrated?

124 Best practices, General Memory = 2x data set Total IOPS = Workload IOPS * 3 Can tlog handle new throughput?

125 Best practices, Native compilation Ordinal parameters Data types must match

126 Best practices, Indexing Range index first Index ALL Foreign Keys Bucket count = Unique * 2 Verify chain length (HASH) Recompile NC after update stats/data changes

127 Best practices, Indexing Range index first Index ALL Foreign Keys Bucket count = Unique * 2 Verify chain length (HASH) Recompile NC after update stats/data changes

128 Best practices, Alerting Checksum failure: Regular processing Checksum failure: Backup/Restore Checksum failure: Database recovery someone updated before you repeatable read validation failure serializable validation failure transaction dependency failure

129 Best practices, Monitoring Resource Group threshold (EE only) Garbage Collection Total memory-optimized data set size Temporal - hidden staging table size

130 Best practices, Planning 1. Identify bottleneck(s) 2. Determine if In-Memory might help 3. POC - identify testing tool(s) 4. Storage architecture design change 5. Test RTO with full data set Repeat Steps 4 and 5 until RTO achieved

131 Best practices, Maintenance Create documentation and test: Redistributing containers (failed RTO) Add container (out of space) PIECEMEAL restore

132 Best practices, ALTER TABLE Test ALTER TABLE in non-prod environment (determine if parallel and minimally logged)

133 Best practices, Resource Groups One RG per memory-optimized db

134 WHITE PAPER

135 White paper review Indexes are never stored on disk

136 White paper review Indexes are never stored on disk

137 White paper review Indexes are never stored on disk DELETE and UPDATE operations will generate row versions

138 White paper review Indexes are never stored on disk DELETE and UPDATE operations will generate row versions

139 White paper review Indexes are never stored on disk DELETE and UPDATE operations will generate row versions Data is on disk to be used when restarting your SQL Server

140 White paper review Indexes are never stored on disk DELETE and UPDATE operations will generate row versions Data is on disk to be used when restarting your SQL Server database

141 White paper review File creation

142 White paper review File creation

143 White paper review File creation 2TB limit

144 White paper review File creation 2TB limit

145 White paper review File creation 2TB limit Parallelism

146 UNSUPPORTED

147 Unsupported features sp_rename Replication publisher/distributor Partitioning (tables/indexes) Bulk/minimal logging Event Notifications DDL triggers Mirroring

148 Unsupported features CDC Compression Cross-database queries/transactions Containment MERGE target Database snapshots More than 8 indexes per table

149 Unsupported data types Computed columns Change tracking CLR (context connection) DDL in transactions Linked servers

150 Unsupported data types datetimeoffset* geography geometry hierarchyid rowversion xml sql_variant* user-defined data types

151 SQL 2017

152 SQL 2017 > 8 indexes per table

153 SQL 2017 > 8 indexes per table NC index rebuild speed improvement

154 SQL 2017 > 8 indexes per table NC index rebuild speed improvement Computed columns (plus indexes)

155 SQL 2017 > 8 indexes per table NC index rebuild speed improvement Computed columns (plus indexes) sp_rename (tables and native modules)

156 SQL 2017 > 8 indexes per table NC index rebuild speed improvement Computed columns (plus indexes) sp_rename (tables and NC modules) sp_spaceused

157 SQL 2017 > 8 indexes per table NC index rebuild speed improvement Computed columns (plus indexes) sp_rename (tables and NC modules) sp_spaceused parallel REDO for AGs

158 SQL 2017 Native Compilation CASE JSON CROSS APPLY

159 Connect items 1. Unknown memory requirements for restoring a backup containing memory-optimized data: 2. Excessive memory usage for memoryoptimized table variable with RANGE index:

160 Connect items 3. DBCC CHECKDB should verify checksums on In- Memory OLTP tables:

161 KEY TAKEAWAYS ARCHITECTURE RTO RESOURCES

162 Real world SQL 2016 In-Memory OLTP e: Ned Otter SQL Strategist #588

The DBA Survival Guide for In-Memory OLTP. Ned Otter SQL Strategist

The DBA Survival Guide for In-Memory OLTP Ned Otter SQL Strategist About me SQL Server DBA since 1995 MCSE Data Platform Passionate about SQL Server Obsessed with In-Memory Key takeaways Recovery (RTO)