switch from block to raw, & modify HP-UX bufcache

Hi everybody, Informix Dynamic Server Version 11.70.FC1GE on HP-UX v11.11 (Risc) I am not a HP-UX admin, and it's been a long time since I've dealt with an Informix engine on block devices (I inherited, I didn't build it). I am seeking advice on whether my improvement plan below is going to work... background: I have recently discovered an HP-UX configuration issue causing both Informix and unix performance issues. There is 8 GB of physical memory, the unix i/o buffer cache is currently set to 4 GB (i believe this is a default setting, set to 50% of memory). Informix is the main application running on this box but starts up with only 960MB of memory/buffer cache. i did not dare increase it yet as OAT tells me there is less than 100MB of free memory on the box. (OAT has been very helpful). A couple weeks ago, while doing a large load, the Informix engine asked for another 500MB of memory. Unix gave the memory using swap space, but then began suffering significant performance problems resulting in a reboot. HP support has since advised me to reduce the unix i/o cache to 1 GB, freeing up 3 GB of memory. I desire to start informix up with a larger buffer cache, but i believe i should first move informix from block device paths to raw device paths. we do ontape level 0 backups every night. we do not have a huge problem getting maintenance outages and our DB is not real big. my plan is (does this make sense, you think it will work?): 1) do an ontape restore, renaming the block device chunk paths to links that point to the raw device paths - i believe this will then free up informix DB demands of the O/S buffer cache by going direct to disk instead of O/S buffering 2) now that informix is bypassing the unix buffercache, i can decrease the size of unix buffercache from 4GB down to 1GB as suggested by HP 3) having freed up approx 3 GB of memory, i can easily adjust Informix config to start up with 2GB of shared memory instead of the current 960MB. Do you think this will work? See any holes in my logic? I have an open ticket with both HP and IBM Informix but have not heard back from either regarding my plan... thanks for your feedback, Norma Jean Sebastian

Looks sound Norma Jean. Art Art S. Kagel Advanced DataTools (www.advancedatatools.com) Blog: http://informix-myview.blogspot.com/ Disclaimer: Please keep in mind that my own opinions are my own opinions and do not reflect on my employer, Advanced DataTools, the IIUG, nor any other organization with which I am associated either explicitly, implicitly, or by inference. Neither do those opinions reflect those of other individuals affiliated with any entity with which I am affiliated nor those of the entities themselves. On Wed, May 25, 2011 at 8:53 PM, NORMA JEAN SEBASTIAN <nj.sebby@gmail.com>wrote: > Hi everybody, > > Informix Dynamic Server Version 11.70.FC1GE > on HP-UX v11.11 (Risc) > > I am not a HP-UX admin, and it's been a long time since I've dealt with an > Informix engine on block devices (I inherited, I didn't build it). > > I am seeking advice on whether my improvement plan below is going to > work... > > background: > > I have recently discovered an HP-UX configuration issue causing both > Informix > and unix performance issues. > There is 8 GB of physical memory, the unix i/o buffer cache is currently > set > to 4 GB (i believe this is a default setting, set to 50% of memory). > Informix is the main application running on this box but starts up with > only > 960MB of memory/buffer cache. i did not dare increase it yet as OAT tells > me > there is less than 100MB of free memory on the box. (OAT has been very > helpful). > > A couple weeks ago, while doing a large load, the Informix engine asked for > another 500MB of memory. Unix gave the memory using swap space, but then > began > suffering significant performance problems resulting in a reboot. > > HP support has since advised me to reduce the unix i/o cache to 1 GB, > freeing > up 3 GB of memory. > > I desire to start informix up with a larger buffer cache, but i believe i > should first move informix from block device paths to raw device paths. > > we do ontape level 0 backups every night. we do not have a huge problem > getting maintenance outages and our DB is not real big. > > my plan is (does this make sense, you think it will work?): > > 1) do an ontape restore, renaming the block device chunk paths to links > that > point to the raw device paths > > - i believe this will then free up informix DB demands of the O/S buffer > cache > by going direct to disk instead of O/S buffering > 2) now that informix is bypassing the unix buffercache, i can decrease the > size of unix buffercache from 4GB down to 1GB as suggested by HP > 3) having freed up approx 3 GB of memory, i can easily adjust Informix > config > to start up with 2GB of shared memory instead of the current 960MB. > > Do you think this will work? See any holes in my logic? > > I have an open ticket with both HP and IBM Informix but have not heard back > from either regarding my plan... > > thanks for your feedback, > Norma Jean Sebastian > > > > ******************************************************************************* > Forum Note: Use "Reply" to post a response in the discussion forum. > > --bcaec50166b779fdec04a4239b51

in regards to memory we have set the kernal parameters as such dbc_max_pct 25 25 Immed dbc_min_pct 5 Default Immed You could probbaly even set dbc_max_pct to 20 Always best to let database engine do caching rather than the operating system for datbase servers ?