Managing Large Databases in the R/3 Environment

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1 TechEd 2000 Hamburg Managing Large Databases in the R/3 Environment Dr. Christian Graf SAP AG

2 TechEd 2000 Hamburg Topics: Disk Layout Shared Memory (32/64 Bit) Performance Analysis / DB Tuning Backup Strategies

3 TechEd 2000 Hamburg Disk Layout rootdbs psapddic psapload psapstab psappool psapprot psapbtab psapsource psapclu psapuser1 psapdoku logdbs physdbs mirrored Dbspace mirrored Dbspace tmpdbs1.

4 Standard Installation Standard R/3 Installation with Informix 7.x Dbspaces / chunks randomly allocated to disks Attached indexes (data and indexes in the same dbspace) No table fragmentation Limitations / disadvantages Maximum table size 32 GB (data + indexes) Hot spots on single disks Hot spots moving over time Runtime problems with administrative tasks (update statistics, drop/create index, oncheck)

5 Traditional Solutions Load distribution by means of: Individual dbspaces for specific tables Detached indexes Table fragmentation tables tables indexes tables tables tables tables indexes tables views

6 Traditional Fragmentation Traditional fragmentation recommendation: Each table fragment resides in its own dbspace! Advantage: Table growth without extent scattering Limitations: Confusing dbspace/chunk layout if used for many tables Difficult to achieve stable I/O balancing Detailed space monitoring required (many dbspaces) Possible waste of disk space

7 Data Balancing Fragment all growing and heavily accessed tables Use 1 set of fragment dbspaces for all fragmented tables (for example, psapcust1,... psapcust<n>) Allocate each fragment dbspace to a different physical disk Use separate index dbspace(s) Same number of fragments for all tables Data distributed over all disks

8 Example DB DA1 DA2 DA3 DA4 DA5 DA6 DA7 DA8 psapcust1 psapcust2 psapcust3 psapcust4 psapcust5 psapcust6 psapcust7 psapcust8 stripeset Psapbtab Psapdoku stripeset stripeset stripeset Psapindex stripeset 1 stripeset Rootdbs (Original) Physdbs (Original) Tempdbs 1 stripeset Stripeset 1 psapcust9 psapcust psapcust11 psapcust12 psapcust13 psapcust14 psapcust15 psapcust16 stripeset stripeset Psapclu Psapddic stripeset stripeset Psapindex stripeset 2 stripeset Rootdbs (Mirror) Physdbs (Mirror) Tempdbs 2 stripeset Stripeset 2 psapcust17 psapcust18 psapcust19 psapcust20 psapcust21 psapcust22 psapcust23 psapcust24 stripeset stripeset Psapstab Psapuser1 Psapload Psapes40B stripeset stripeset Psapindex stripeset 3 stripeset Logdbs (Original) Tempdbs 3 stripeset Stripeset 3 psapcust25 psapcust26 psapcust27 psapcust28 psapcust29 psapcust30 psapcust31 psapcust32 stripeset stripeset Psappool Psapprot Psapsource Psapel40B stripeset stripeset Psapindex stripeset 4 stripeset Logdbs (Mirror) Tempdbs 4 stripeset Stripeset 4

9 Advantages I/O load evenly distributed: Over all disks Over all controllers No hot spots Exploits whole capacities of disk subsystem Parallel Database Query possible Speed up administrative tasks Less administrative overhead Easier monitoring Easy to extend * No waste of disk space * as long as the box provides freespace

10 Important Remarks Excessive extent growth must be prevented Extent growth must be monitored (limit ) Adapt next extent sizes if necessary Ensure appropriate contiguous free disk space on raw devices! Avoid dbspace reorganization as much as possible! Fragmentation imposes an overhead on table accesses Do not fragment small tables

11 TechEd 2000 Hamburg More Details in SAP White Paper: Database Layout for SAP Installations with Informix

12 TechEd 2000 Hamburg Shared Memory 32-Bit Limits SHM_MAGIC for HP-UX 64-Bit Availability (Database/Kernel)

13 Shared Memory Shared Memory 32-Bit Limits HP- UX 1,75 GB (Server) SOLARIS 3,50 GB (R/3 Instance, DB) AIX 2,75 GB SINIX 1,60 GB (R/3 Instance, DB) Windows NT 2,50 GB (Enterprise Edition)

14 Shared Memory Workaround for HP-UX 32-Bit Shared Memory Magic (SHMEM_MAGIC) 1 GB memory quadrant usually used for data segments is reserved for shared memory Available for HPUX.20 (patch needed) and 11.0 Special R/3 kernel required ( sapserv ) DB executables must be treated with chatr -M command Next upgrade requires 64-bit kernel More details: OSS Note 6819 Only supported/recommended for 3.1I DCK kernel 4.x customers must use 64-bit kernel/db version

15 Shared Memory 64-Bit Informix DB Availability HPUX FC7XK1 SOLARIS FC7A AIX FC7XK SINIX FC DEC TRUE 64: 7.31.FC4A Available for 3.1x (3.1I DCK), 4.0B, 45B, 46B,... Ordering 64-bit DB CDs: OSS note

16 Shared Memory 64-Bit R/3 Kernel Availability HPUX B, 45B, 46B OSF/1: all kernel 64-Bit SOLARIS: planed in 2000 AIX planed in 2000 SINIX B, 45B, 46B General information on SAP 64-bit strategy:

17 TechEd 2000 Hamburg Performance Analysis / DB Tuning

18 Performance Analysis / DB Tuning General approach for performance analysis: Early Watch sessions CCMS monitoring transactions (st03, st04, db02) Tracing long-running SQL statements using st05 DB monitoring using onstat tool (memory, I/O, etc.)

19 General DB Tuning I/O balancing Shared memory ❿ BUFFER size: Read: >= 96 % Write: >= 82 % (onstat -p) ❿ SHMVIRTSIZE: = Size of virtual portion (st04) only one virtual segment! Onconfig parameter (DB and instances on different hosts): ❿ CPU VPs: (>2 CPU s: NUMCPUVPS = #CPU s - 1(2)) ❿ LRU queues NUMCPUVPS + 2 ❿ Page cleaners LRU s * 2 (testing required) ❿ Number of locks (<= 30% of total SHM)

20 Specific DB Tuning Analyze query runtimes using st05 : Actions: Identify long-running statements Remove first_rows parameter from R/3 profile if exists Remove opt_goal parameter from onconfig profile if exists Provide query plan (SQL explain [st05, dbaccess]) Is the query plan appropriate? Adequate access strategy (table scan, nested loop join, hash join,..)? Appropriate indexes used/available? Specific update statistics scenario on table(s) required? Hint required for optimal query plan?

21 TechEd 2000 Hamburg Backup Strategies

22 Backup Strategies Ontape Size of R/3 Databas e ON-Archive ON-Bar EBR Single De vice Sequential Devices Parallel Devices 18GB 70GB 200G 500GB Backup Devices

23 Informix Backup Tools Ontape ON-Archive ON-Bar Simple to use Sequential backups only No tape management No API to storage management systems Backups and recovery on dbspace level Sequential and parallel backups and recovery Tape management Software compression and backup encryption Automatic backups (unattended operation) Event tracking with the sysmaster database Point-in-time recovery All ON-Archive functions Simpler to use than ON-Archive Standardized interface (X/BSA) for storage management systems from other vendors Will become default backup tool of Informix

24 Backup Strategies Database sizes up to 200 GB Use of ON-Archive/ON-Bar Full level-0 backup once a week during off-peak hours Level-1 backup during weekdays Level-2 backup for second half of week if required Automatic logical-log backup ideally to one specific tape/day ALARMPROGRAM technique to prevent log overflow during load peaks (for example, batch input) Logical-log size: 1-4 GB depending on daily workload

25 Backup Strategies Database sizes up to 500 GB Use of ON-Bar Take advantage of high-performance storage managers Parallel backup of equally sized dbspacesets Nearly linear scaling in multiprocessor environments Incremental parallel backups if required List of supported storage managers (ON-Bar) see white paper : Backup Concepts for SAP R/3 Systems on Informix IDS

26 External Backup and Restore Database sizes beyond 500 GB Backup based on split mirror technique Primary Disks rootdbs psapstab psapbtab onmode -c block/unblock: ❿ Synchronize disk memory rootdbs psapstab psapbtab ❿ Detach/split mirror ❿ Backup on mirrored disks Mirror Disks ❿ Resynchronize main and mirror disk set afterwards Downtime: a few seconds/minutes for detaching mirror Enterprise storage system required that offers mirror detaching Complex, but most powerful for terabyte databases

27 Example FDDI Backbone Primary Database Server Shared SCSI Tape Robot Secondary Database Server 8xSCSI Secondary SCSI connections 8xSCSI EMC² Box 1 EMC² Box 2 FSP-1 F ile S y s te m P a rtitio n SRDF FSP-2 File System Partition RAID 1/Mirror ID S -1 R AID 1 /Mirro r SRDF BCV ID S -2 ID S -3

28 TechEd 2000 Hamburg Further Information... White papers Presentations (TechED 2000) Supported IDS Versions Notes...

29 TechEd 2000 Hamburg Discussion...

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