AIX Configuration & Tuning for Oracle DB

8/10/2019 AIX Configuration & Tuning for Oracle DB

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8/29/2008 2006 IBM Corporation

AIX Configuration & Tuning for Oracle DB

IBM Advanced Technical Support


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Basic AIX Configuration/Tuning for OraclePreparing the runtime environmentMemory

I/O

Network

Agenda


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The suggestions presented here are consideredto be basic configuration starting points forgeneral Oracle workloads

Customer workloads will varyOngoing performance monitoring and tuning isrecommended to ensure that the configuration isoptimal for the particular workload

characteristics

AIX Configuration for Oracle starting points


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Preparing the runtime environment

User Limits (smit chuser)Soft FILE size = -1 (Unlimited)

Soft CPU time = -1 (Unlimited)

Soft DATA segment = -1 (Unlimited)

Soft STACK size -1 (Unlimited)

/etc/security/limits

Maximum number of PROCESSES allowed per user (smit chgsys)maxuproc >= 2048


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VMM File System Cache Tuning (vmo)File System related parameter defaults are optimized for large file

system cache, not for RDBMS workloadsTypical vmo settings for Oracle:

lru_file_repage=0 (default=1) (AIX 5.2 ML04 or later)Forces file pages to be repaged before computational pages

minperm%=5 (default 20)Target for minimum % of physical memory to be used for file systemcache

maxperm%=20 ( default 80)

Target for maximum % of physical memory to be used for JFS filesystem cache

strict_maxperm=0 (the default)Enables/disables enforcement of maxperm as a hard limit

maxclient%=20 (the default 80)maxclient=maxpermTarget for maximum % of physical memory to be used for JFS2 file

system cachestrict_maxclient=1 (the default) (AIX 5.2 ML04 or later)


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VMM Page Stealing Thresholds

The following define thresholds for the VMM page stealing process (lrud):minfree

Set minfree = 120 x # logical CPUs

maxfree

Set maxfree = minfree + (MAX(maxpgahead, j2_maxPageReadAhead) x

# logical CPUs)

Example:

For a 6-way LPAR with SMT enabled, maxpgahead=8 and j2_maxPageReadAhead=8 :

minfree = 1440 = 120 x 6 x 2maxfree = 1536 = 1440 + (max(8,8) x 6 x 2)

vmo o minfree=1440 o maxfree=1536 -p



AIX Paging Space

Allocate Paging Space:

Configure Server/LPAR with enough physical memory to satisfy memory requirementsWith AIX demand paging, paging space does not have to be large

Generally, keep within internal drive

Monitor paging activity :

vmstat -s

sar -r Lsps a

Resolve paging issues:

Reduce file system cache size (LRU_FILE_REPAGE, MAXPERM, MAXCLIENT)

Reduce Oracle SGA or PGA (9i or later) size

Add physical memory

SGA may be pinned on AIX, but not generally recommended

vmo p o v_pinshm=1

LOCK_SGA=TRUEDo not overcommit real memory!



CPU Considerations

Use SMT with AIX 5.3environments#smtctl -m on -w now



DLPAR & Oracle

CPUOracle 9i

Oracle CPU count does not recognize change in # cpus

AIX scheduler can still use the added CPUs

Oracle 10g

Oracle CPU count recognizes change in # cpus

MemoryOracle 9i or 10g

SGA can be dynamically resized, but has an upper boundby the parameter SGA_MAX_SIZE.


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Data Layout for Optimal I/O Performance

Stripe and mirror everything (SAME) approach:

Goal is to balance I/O activity across all disks, loops, adapters, etc...

Avoid/Eliminate I/O hotspots

Manual file-by-file data placement is time consuming, resource intensive anditerative

Use RAID-5 or RAID-10 to create striped LUNs (hdisks)

Create AIX Volume Group(s) (VG) w/ LUNs from multiplearrays, striping on the front end as well for maximumdistribution

Physical Partition Spreading (mklv e x) or-

Large Grained LVM striping (>= 1MB stripe size)

http://www-1.ibm.com/support/techdocs/atsmastr.nsf/WebIndex/WP100319


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Data Layout contd

Stripe using Logical Volume (LV) or Physical Partition (PP) striping

LV Striping

Valid LV Strip sizes:

AIX 5.2: 4k, 8k, 16k, 32k, 64k, 128k, 256k, 512k, 1 MBAIX 5.3: AIX 5.2 Strip sizes + 2M, 4M, 16 MB, 32M, 64M, 128M

Use AIX Logical Volume 0 offset (9i Release 2 or later)Use Scalable Volume Groups (VGs), or use mklv T O with BigVGsThe -T O option specifies that the device subtype should be z, whichcauses Oracle to use a zero offset when accessing this raw logicalvolume

PP Striping

Use minimum Physical Partition (PP) size (mklv -t, -s parms)

Spread AIX Logical Volume (LV) PPs across multiple hdisks in VG(mklv e x)


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Asynchronous I/OAIX parameters (smit aio) -- only applicable to file system based configs

minservers = 10 * # cpusmaxservers = (10 * # disks) / # cpusmaxreqs = a multiple of 4096 > 4 * #disks * queue_depthenable at system restartTypical settings: minservers=100, maxservers=100,maxreqs=16384

Oracle parameters (init.ora)

disk_asynch_io = TRUEfilesystemio_options = {ASYNCH | SETALL}

Monitor usage:

Watch for Oracle alert log or trace file messages:Warning lio_listo returned EAGAIN

AIX Monitoringpstat a | grep aiosiostat A (AIX 5.3)NMON -A and -t options


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AIX File SystemsJournaled File System (JFS)

Buffer caching (default) provides Sequential Read-Ahead, cached writes, etc.Direct I/O (DIO) mount/open option no caching on reads

No longer being enhanced

Enhanced JFS (JFS2)

Buffer caching (default) provides Sequential Read-Ahead, cached writes,etc.

Direct I/O (DIO) mount/open option no caching on reads

Concurrent I/O (CIO) mount/open option DIO, with write serializationdisabled

Use CIO for Oracle .dbf, control files and online redo logs only!!!

General Parallel File System (GPFS)

Non-cached, non-blocking I/Os (similar to JFS2 CIO) for all Oracle files

The IBM clustered file system for RAC GPFS, or JFS2 with CIO offer similar performance as Raw Devices


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Cached vs. non-Cached (Direct) I/O

Set filesystemio_options=SETALL-or-

Use cio mount option

Use cio mount optionJFS2


Use dio mount option


Use dio mount optionJFS

Oracle 10gOracle 9i

File System caching tends to benefit heavily sequential workloads with lowwrite content. To enable caching for JFS/JFS2:

Use default filesystem mount options

Set Oracle filesystemio_options=ASYNCH

DIO tends to benefit heavily random access workloads and CIO tends tobenefit heavy update workloads. To disable JFS, JFS2 caching, see thefollowing table:


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Oracle Database File Access

Data Base Files (DBF)I/O size is db_block_size or db_block_size * db_file_multiblock_read_count

Use CIO or no mount options for extremely sequential I/O

If block size is >=4096, use a filesystem block size of 4096, else use 2048

Redo Log/Control FilesI/O size is always a multiple of 512 bytes

Use CIO or DIO and set filesystem block size to 512

Archive Log FilesDo not use CIO or DIO

rbrw mount option can be advantageous

Oracle BinariesDo not use CIO or DIO


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Network Options (no) Parameters

Set sb_max >= 1 MB (1048576)

Set tcp_sendspace >= 262144

Set tcp_recvspace >= 262144

Set rfc1323 =1

Also confirm these are set properly at network interfacelevel


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Additional Network (no) Parameters for RAC:Set udp_sendspace = db_block_size *db_file_multiblock_read_count

(not less than 65536)

Set udp_recvspace = 4 * udp_sendspace

Must be < sb_maxIncrease if buffer overflows occur

Use Jumbo Frames

Examples:no -a |grep udp_sendspace

no o -p udp_sendspace=65536

netstat -s |grep "socket buffer overflows"


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Oracle Information Sources - External

Oracle Product Certification information: http://otn.oracle.com/support/metalink/index.html

Oracle Pricing Information:

http://store.oracle.com/

Oracle Technology Network

http://otn.oracle.com

IBM Redbooks:

http://www.ibm.com/redbooks Techdocs Technical Sales Library

http://w3.ibm.com/support/techdocs

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AIX Configuration & Tuning for Oracle DB