TBLSPACE_STAT / LBU_PRESERVE
Hi Users, I am working on Sun Solaris 2.51 / IDS 7.3. Have some queries for which have not found answers in Informix Answers Online : 1. TBLSPACE_STAT set to 1 in ONCONFIG .... what is its use. 2. We use continous backup , so do we need to set LBU_PRESERVE TO 1. How does this parameter really help. It only avoids a dead-lock , but how does the DBA know that all but 1 logs are full ???? 3. We have a EMC 18 GB disk rack with 18 GB for mirror. We have a 2 GB chunk for tmpdbs to do our DW queries. Would we have a performance improvement if we spread out the temporary database to 2-3 X 2GB tmpdbs(1,2,3) ??? Thanks in advance for Ur responses... Prashant ______________________________________________________ Get Your Private, Free Email at http://www.hotmail.com
Prashant, As for question 3, yes, multiple tempdbspaces should improve your performance somewhat. Informix will spread temp tables across however many tempdbs' you have, and you can take advantage of some parallelism. Just be sure to list all of your tempdbs' in the DBSPACETEMP configuration parameter. Kind regards, John Bejarano. >3. We have a EMC 18 GB disk rack with 18 GB for mirror. We have a 2 GB chunk >for tmpdbs to do our DW queries. Would we have a performance improvement if >we spread out the temporary database to 2-3 X 2GB tmpdbs(1,2,3) ??? > >Thanks in advance for Ur responses... > >Prashant > > >______________________________________________________ >Get Your Private, Free Email at http://www.hotmail.com
> > 1. TBLSPACE_STAT set to 1 in ONCONFIG .... what is its use. > TBLSPACE_STAT is undocumented Informix param, that is used by Informix Tech Support in debugging reasons. Do not set it in production environment. > 2. We use continous backup , so do we need to set LBU_PRESERVE TO 1. How > does this parameter really help. It only avoids a dead-lock , but how does > the DBA know that all but 1 logs are full ???? > This param doesn't help you to avoid logs to be filled. Consider the following example : Informix detects long transaction and becomes to rollback. But rollback takes log space too. If you have purely configured LTXHWM and LTXEHWM, all your logs can be completely filled. And in this case logs is not backed up, because open transaction is there. The only way to correct this situation without any losses is to add another log. But the log addition is logged too. If you have LBU_PRESERVE set to 1, you have 1 log for this purpose. So, in this case you are able to add log to complete the rollback of entire transaction. > 3. We have a EMC 18 GB disk rack with 18 GB for mirror. We have a 2 GB chunk > for tmpdbs to do our DW queries. Would we have a performance improvement if > we spread out the temporary database to 2-3 X 2GB tmpdbs(1,2,3) ??? Of course. It's even better to move tempdbspace to non-mirrored disks, cause this dbspaces is not critical to the server's operation. -------------------------------- With best regards, Yuri Dovgart. Sent via Deja.com http://www.deja.com/ Share what you know. Learn what you don't.
> > 1. TBLSPACE_STAT set to 1 in ONCONFIG .... what is its use. > TBLSPACE_STAT is undocumented Informix param, that is used by Informix Tech Support in debugging reasons. Do not set it in production environment. > 2. We use continous backup , so do we need to set LBU_PRESERVE TO 1. How > does this parameter really help. It only avoids a dead-lock , but how does > the DBA know that all but 1 logs are full ???? > This param doesn't help you to avoid logs to be filled. Consider the following example : Informix detects long transaction and becomes to rollback. But rollback takes log space too. If you have purely configured LTXHWM and LTXEHWM, all your logs can be completely filled. And in this case logs is not backed up, because open transaction is there. The only way to correct this situation without any losses is to add another log. But the log addition is logged too. If you have LBU_PRESERVE set to 1, you have 1 log for this purpose. So, in this case you are able to add log to complete the rollback of entire transaction. > 3. We have a EMC 18 GB disk rack with 18 GB for mirror. We have a 2 GB chunk > for tmpdbs to do our DW queries. Would we have a performance improvement if > we spread out the temporary database to 2-3 X 2GB tmpdbs(1,2,3) ??? Of course. It's even better to move tempdbspace to non-mirrored disks, cause this dbspaces is not critical to the server's operation. -------------------------------- With best regards, Yuri Dovgart. Sent via Deja.com http://www.deja.com/ Share what you know. Learn what you don't.
prashant naik wrote: > > Hi Users, > > I am working on Sun Solaris 2.51 / IDS 7.3. Have some queries for which have > not found answers in Informix Answers Online : > > 1. TBLSPACE_STAT set to 1 in ONCONFIG .... what is its use. Your other questions have been answered adequately but... TBLSPACE_STAT 1 enables additional table level statistics gathering in the engine. It is NOT a hidden tech support diagnostic flag, though there are plenty of those around. There IS however a significant overhead penalty for turning this flag on and it is recommended that it normally be kept at zero (0). Art S. Kagel