Aix tuning

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Session Title AIX Performance Tuning for Databases

Jaqui Lynch
Mainline Information Systems

• • • • • • • • • I AM NOT A DBA but I know one  Starter set of tunables Determining what to set tunables to Page space Memorytuning Oracle and disk Volume groups and filesystems Asynchronous and Concurrent I/O Oracle AWR


Starter set of tunables 1/3
Typically we set the following for both versions: NETWORK no -p -o rfc1323=1 p o rfc1323 1 no -p -o sb_max=1310720 no -p -o tcp_sendspace=262144 no -p -o tcp_recvspace=262144 no -p -o udp_sendspace=65536 no -p -o udp_recvspace=655360 Also check the actual NICinterfaces and make sure they are set to at least these values


ifconfig -a output
en0: flags=1e080863,480 inet netmask 0xfffffe00 broadcast tcp_sendspace 65536 tcp_recvspace 65536 lo0: flags=e08084b inet netmask 0xff000000 broadcast inet6 ::1/0 tcp_sendspace 131072 tcp_recvspace 131072 rfc1323 1 These override no, so they will need to beset at the adapter. Additionally you will want to ensure you set the adapter to the correct setting if it runs at less than GB, rather than allowing auto-negotiate Stop inetd and use chdev to reset adapter (i.e. en0)


Interface lo0 Ethernet Ethernet Ethernet Ethernet Ethernet Virtual Ethernet InfiniBand Speed N/A 10/100 mb 1000 (Gb) 1000 (Gb) 1000 (Gb) 1000 (Gb) N/A N/A MTU 168961500 9000 1500 9000 any 2044 tcp_sendspace 131072 131072 262144 262144 262144 262144 131072 tcp_recvspace 131072 165536 131072 262144 262144 262144 131072 rfc1323 1 1 1 1 1 1 1

Above taken from Page 247 SC23-4905-04 November 2007 edition Check up to date information at: d/prftungd.pdf d/ ft d df

5Starter set of tunables 2/3
For AIX v5.3
No need to set memory_affinity=0 after 5.3 tl05

vmo -p -o minperm%=3 p o minperm% 3 vmo -p -o maxperm%=90 vmo -p -o maxclient%=90 vmo -p -o minfree=960 vmo -p -o maxfree=1088 vmo -p -o lru_file_repage=0 vmo -p -o lru_poll_interval=10 The parameters below should be reviewed and changed (see vmstat –v and lvmo –a later) PBUFS ioo -p -opv_min_pbuf=1024 – old way – use the new way (next slide) JFS2 ioo -p -o j2_maxPageReadAhead=128 j2_dynamicBufferPreallocation=16 Default that may need tuning Replaces tuning j2_nBufferPerPagerDevice JFS ioo -p -o numfsbufs=1024 ioo -p -o maxpgahead=16



numfsbufs (JFS) Purpose: Specifies the number of file system bufstructs bufstructs. Values: Default: 196 (value is dependent onthe size of the bufstruct) Type: Mount Increase based on vmstat –v output 39943187 filesystem I/Os blocked with no fsbuf Numbers here mean that VMM queued the I/O as if could not get a free bufstruct for it. In AIX v6 this becomes a restricted variable


The number of 16k chunks to preallocate when the filesystem is running low of bufstructs. Old method – tunej2_nBufferPerPagerDevice Minimum number of file system bufstructs for Enhanced JFS. New method Leave j2_nBufferPerPagerDevice at the default Increase j2_dynamicBufferPreallocation as needs be. 16k slabs, per filesystem and requires a filesystem remount. vmstat –v Increase if "external pager filesystem I/Os blocked with no fsbuf“ increases I/O load on the filesystem may be exceeding the speed ofpreallocation.



pv_min_pbuf Purpose: Specifies the minimum number of pbufs per PV that the LVM uses. This is a global value that applies to all VGs on the system. Values: Default: 256 on 32-bit kernel; 512 on 64-bit kernel. Range: 512 to 2G-1 Type: Dynamic vmstat –v "pending disk I/Os blocked with no pbuf“ Indicates that the LVM had to block I/O requests waiting for pbufs...
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