Re: onmode -F

Zeljan Silje wrote: > > Hi, > > in "Performance Guide Version 7.2" I found recommandation to run onmode > -F using cron facility. > Does anyone has experience with this, and how often should I execute > onmode -F using cron?> I am using Informix OnLine7.22 on AIX4.2. > > Thanks in advance, > Zeljan > onmode -F frees unused memory segments The answer depends entirely on how your system is being used (like all performance and tuning questions). Look to see how often your system is allocating additional memory segments (in the online log). The message will be something like: 08:32:42 dynamically allocated new shared memory segment (size 8388608) Run onstat - to find out the resident memory size. Next, run an onmode -F followed by an onstat - to find out the new resident size. If it is significantly lower, then consider running onmode -F every night (or when the system load is low if night is a bad time). Also look at the output of onstat -g seg (see manual). If you find that there is a lot of additional memory being allocated but not being released with an onmode -F then it is likely that it is being utilised. If so, consider increasing the SHMADD $ONCONFIG parameter, to allow informix to allocate more memory in one operation. Conversely, if memory is being allocated but is available for release soon after, it is possible that the total allocation is not being used. Then consider decreasing the SHMADD parameter. You should also examine the system from the AIX perspective, using the ipcs command, to check that any shared memory used by informix for interprocess communcation is being released correctly. As you can see, the answer is not a simple one and requires knowledge of both how the both OnLine engine and AIX operate. Hope this information is useful. Dan P.S. (To all readers) To the best of my knowledge this reply is correct. If it is not, please post corrections.