Essbase Using Swap Memory - Degraded Performance

Question

Currently on Essbase 6.5.4.2 and Sun Solaris 5.8I find that when the server is running very low on Physical RAM and needs to use Swap during any Essbase Calculation that calc time performance is severly degraded. Is this a functionality of Essbase or a setting in UNIX that can be altered?I'm not a UNIX admin and I need to know how to approach my IT group with this.Thanks!

Answer 1

Yes, that's to be expected. performance always degrades once swap file is used due to the i/o bottleneck of swapping ram to disk and back. The easiest solution is to prevent your applications running out of ram memory. I've noticed that applications grow in memory through use to some huge sizes, so I unload them from memory at least three times a day so that they load back nice and compact. I've set up a script to do this automatically at the beginning of the day, at midday and at the end. You can also manage memory manually, eg. if you need to run a major calculation, then unload all other applications, then unload that application and reload it before the calc.You can also try to use direct i/o. there is a Unix setting that you can switch to direct i/o, but it caused us problems and corrupted the databases, so use the Essbase database settings. On Solaris you need the root user to run the script 'root.sh', then it will become available. In database/settings, under storage, change the access to direct i/o and tick cache memory locking. You als have to assign a data file cache and reduce your data cache as it doesn't need to be so big about 10% of the data file cache. This will ensure that that database will allways have priority for ram and not use the swap file. The manual recommends that you use buffered i/o instead of direct i/o, but I think it is a matter of judgement. If you need it, then use it. We've been using it without problems. Make sure that your applications using direct i/o don't assign more memory than is available, otherwise it will go back to swap file. The log file will tell you if is is using direct i/o when an application loads.