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Full Discussion: High memory usage in AIX 5.1
Operating Systems AIX High memory usage in AIX 5.1 Post 302167516 by bakunin on Thursday 14th of February 2008 04:31:14 PM
Old 02-14-2008
Quote:
Originally Posted by jayakumarrt
Thanks for the reply.One thing i am wondering.Sometime back the server was having 4GB ram and recently upgraded to 8 GB.Before upgrading from 4 to 8 GB RAM it was showing 99% memory usage & after upgradation also the same case..

Can anybody throw light on this. ?
If you have the output of "vmstat" from before the upgrade ready have a look at it: i bet you will see a lot of swapping going on and probably now you won't see any (or at least much less than before). The same is perhaps true for the output of "lsps -a", which tells you about the utilization of the swapspaces: perhaps the numbers decreased steeply after upgrading the RAM.

UNIX tries to use the RAM given to it as efficiently as possible: First all the processes started get the memory they need. Some memory is set aside for network buffers, file cache, etc. If still memory is available these buffers will increase in size - which buffers increases how much depends on how the machine is used: more disk-I/O, more network traffic, etc.. The administrator can tune the kernel built-in heuristics with the tools vmo (virtual memory options), schedo (scheduler options), no (network options) and ioo (I/O-options). See the manpages of these tools and the documentation of /etc/tunables for more information.

If no memory is available after satisfying the started processes demands paging occurs: memory pages are taken from the "computational memory" (memory occupied by programs by swapping them out to the paging space) or from the "file memory" (the file cache). When and how much is taken from what can also be tuned, see the "maxperm" and "minperm" parameters in "vmo".

Of course i cannot give you a detailed documentation of the AIX kernel here: what i wrote above are only glimpses and pretty unsorted ones. If you are interested in the details there are two IBM classes (AIX System Administration III: Performance Tuning; AIX Kernel Internals; each 5 days). There are also Redbooks (IBM Redbooks | AIX 5L Practical Performance Tools and Tuning Guide, IBM Redbooks | AIX 5L Performance Tools Handbook, IBM Redbooks | Database Performance Tuning on AIX) available, read them for further details.

I hope this helps.

bakunin
 

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PERLOS400(1)						 Perl Programmers Reference Guide					      PERLOS400(1)

NAME
perlos400 - Perl version 5 on OS/400 DESCRIPTION
This document describes various features of IBM's OS/400 operating system that will affect how Perl version 5 (hereafter just Perl) is compiled and/or runs. By far the easiest way to build Perl for OS/400 is to use the PASE (Portable Application Solutions Environment), for more information see <http://www.iseries.ibm.com/developer/factory/pase/index.html> This environment allows one to use AIX APIs while programming, and it provides a runtime that allows AIX binaries to execute directly on the PowerPC iSeries. Compiling Perl for OS/400 PASE The recommended way to build Perl for the OS/400 PASE is to build the Perl 5 source code (release 5.8.1 or later) under AIX. The trick is to give a special parameter to the Configure shell script when running it on AIX: sh Configure -DPASE ... The default installation directory of Perl under PASE is /QOpenSys/perl. This can be modified if needed with Configure parameter -Dprefix=/some/dir. Starting from OS/400 V5R2 the IBM Visual Age compiler is supported on OS/400 PASE, so it is possible to build Perl natively on OS/400. The easier way, however, is to compile in AIX, as just described. If you don't want to install the compiled Perl in AIX into /QOpenSys (for packaging it before copying it to PASE), you can use a Configure parameter: -Dinstallprefix=/tmp/QOpenSys/perl. This will cause the "make install" to install everything into that directory, while the installed files still think they are (will be) in /QOpenSys/perl. If building natively on PASE, please do the build under the /QOpenSys directory, since Perl is happier when built on a case sensitive filesystem. Installing Perl in OS/400 PASE If you are compiling on AIX, simply do a "make install" on the AIX box. Once the install finishes, tar up the /QOpenSys/perl directory. Transfer the tarball to the OS/400 using FTP with the following commands: > binary > site namefmt 1 > put perl.tar /QOpenSys Once you have it on, simply bring up a PASE shell and extract the tarball. If you are compiling in PASE, then "make install" is the only thing you will need to do. The default path for perl binary is /QOpenSys/perl/bin/perl. You'll want to symlink /QOpenSys/usr/bin/perl to this file so you don't have to modify your path. Using Perl in OS/400 PASE Perl in PASE may be used in the same manner as you would use Perl on AIX. Scripts starting with #!/usr/bin/perl should work if you have /QOpenSys/usr/bin/perl symlinked to your perl binary. This will not work if you've done a setuid/setgid or have environment variable PASE_EXEC_QOPENSYS="N". If you have V5R1, you'll need to get the latest PTFs to have this feature. Scripts starting with #!/QOpenSys/perl/bin/perl should always work. Known Problems When compiling in PASE, there is no "oslevel" command. Therefore, you may want to create a script called "oslevel" that echoes the level of AIX that your version of PASE runtime supports. If you're unsure, consult your documentation or use "4.3.3.0". If you have test cases that fail, check for the existence of spool files. The test case may be trying to use a syscall that is not implemented in PASE. To avoid the SIGILL, try setting the PASE_SYSCALL_NOSIGILL environment variable or have a handler for the SIGILL. If you can compile programs for PASE, run the config script and edit config.sh when it gives you the option. If you want to remove fchdir(), which isn't implement in V5R1, simply change the line that says: d_fchdir='define' to d_fchdir='undef' and then compile Perl. The places where fchdir() is used have alternatives for systems that do not have fchdir() available. Perl on ILE There exists a port of Perl to the ILE environment. This port, however, is based quite an old release of Perl, Perl 5.00502 (August 1998). (As of July 2002 the latest release of Perl is 5.8.0, and even 5.6.1 has been out since April 2001.) If you need to run Perl on ILE, though, you may need this older port: <http://www.cpan.org/ports/#os400> Note that any Perl release later than 5.00502 has not been ported to ILE. If you need to use Perl in the ILE environment, you may want to consider using Qp2RunPase() to call the PASE version of Perl. AUTHORS
Jarkko Hietaniemi <jhi@iki.fi> Bryan Logan <bryanlog@us.ibm.com> David Larson <larson1@us.ibm.com> perl v5.18.2 2013-11-04 PERLOS400(1)
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