Re: Strange behaviour with ISM

Hi, ISM is a storage manager that is derived from Legato Networker. As it comes free with IDS, it has some limitations. One of the limitations is that ISM can handle only 4 devices in parallel. Check parameter BAR_MAX_BACKUP in your onconfig file. It determines, how many dbspace objects will be backed up (and restored) in parallel. 0 (zero) means unlimited. Since ISM has this limit of 4 devices, BAR_MAX_BACKUP probably should be set to 3. This will let an onbar command backup (or restore) dbspaces in parallel, but with a maximum parallelism of 3 dbspaces at any time. Therefore one device should remain available for log backup. Thus there should not be a reason for ISM to umount the log backup device. Now, the above is assuming a) that you run only one onbar backup dbspace command at a time. You can run several onbar backup commands in parallel, with different dbspaces listed for each command. In that case each of the backup commands will run up to BAR_MAX_BACKUP processes in parallel. (When executing separate onbar backup commands, they will not coordinate between them.) b) that you have only one IDS instance on the machine doing backup that utilizes ISM. You can have more than one IDS instance utilizing the same ISM instance for backup/restore. (In fact you can have only one ISM instance running on one machine.) If more than one IDS instance does backup (of dbspaces) at the same time, than for each instance the respective BAR_MAX_BACKUP limit does apply. Additionally, if the log backup of the different IDS instances would utilize different pools/media/devices in ISM, then there could be additional "competition" for these ISM resources from log backups of the different IDS instances. Regards, Martin -- Martin Fuerderer IBM Informix Development Munich, Germany Information Management IBM Deutschland GmbH Chairman of the Supervisory Board: Hans Ulrich Märki Board of Management: Martin Jetter (Chairman), Rudolf Bauer, Christian Diedrich, Christoph Grandpierre, Matthias Hartmann, Thomas Fell, Michael Diemer Corporate Seat: Stuttgart, Germany; Reg.-Gericht: Amtsgericht Stuttgart, HRB-Nr.: 14 562 WEEE-Reg.-Nr. DE 99369940 informix-list-bounces@iiug.org wrote on 09.08.2007 09:52:31: > > I have recently had my sleep disturbed on an almost nightly basis > by a repetitive problem with ISM and Onbar. > > We are running ISM and onbar for IDS 10.00.UC5? on AIX 5.3. > > What is happening is that periodically the log backup device > becomes unmounted. There are no errors reported in either the > online.log, the bar_act.log, and the ism daemon.log files. > > Initially this was happening with only one system but now I > have it on two systems. Having done a careful analysis of > the log files involved and UNIX performance statistics I > have discovered that this problem only occurs when the UNIX > i/o throughput is showing very high values. > > If anybody has seen something similar or can suggest how to > proceed with analysis of this problem I would be most grateful. > > Regards > > Malcolm_______________________________________________ > Informix-list mailing list > Informix-list@iiug.org > http://www.iiug.org/mailman/listinfo/informix-list