Re: Logical logs
Girish Punjabi wrote: > > HI Vinodh, > > Nothing wrong with more logical logs except that is is inefficient from > an administrative point of view. > Instead of having 120 logical logs of 2MB each you can have 30 logs of > 8MB each.You can also set LTXHWM & LTXEHWM are 80 and 90 > respectively.We have overcome the long transaction problem here by > deviating from Informix suggested values of 50 and 60. > Also , as William suggested, you need to have a look at the code as > well , as no amount of tuning can help if the code is inefficient. Mmmm, put it this way, if YOU were on technical support, and a customer rang with their system stuck because a long transaction couldn't rollback, and they had increased LTXHWM & LTXEHWM, would YOU have any sympathy for them?? In my experience, lots of small logs (5-10 Mb) are most useful. If your granularity is too large, then the effects of LTXHWM & LTXEHWM are exacerbated. Cheers, -- Mark. +----------------------------------------------------------+-----------+ | Mark D. Stock mailto:mdstock@mydas.freeserve.co.uk |//////// /| | http://www.informix.com http://www.informixhandbook.com |///// / //| | http://www.iiug.org +-----------------------------------+//// / ///| | |This email will self-destruct in |/// / ////| | |10 sec. If you received this email |// / /////| | |in error, sorry about the mess. |/ ////////| +----------------------+-----------------------------------+-----------+
Mark, You are quite correct. SAP instances like mine have 400+ users. SAP suggests having 200 10-MB log files. The previous DBA did not have them alternating from one device to another like I have now but that is the best. I have 4 devices, each having 50 logs, alternating round robin style amongst the four devices. Alternating them will not bottleneck read and write i/o on the device. I have four devices to increase the speed of read/write i/o not only in normal situations but in fast recovery mode in case of a crash. We also have the log dbspaces mirrored, both at the Informix level and at the O/S level. Mirroring also allows reads to occur from the mirrored device as well as the primary. Girish, In the case of long transactions, remember that if someone begins a transaction, walks away from their terminal for lunch -- or simply leaves work to go home for the evening -- you will probably have a long transaction occur. Take care. Have a safe Memorial Day. Remember the fallen ... Clifton Bean "Mark D. Stock" <mdstock@mydas.freeserve.co.uk> wrote in message news:8ghf59$sg6$1@news.xmission.com... > > Girish Punjabi wrote: > > > > HI Vinodh, > > > > Nothing wrong with more logical logs except that is is inefficient from > > an administrative point of view. > > Instead of having 120 logical logs of 2MB each you can have 30 logs of > > 8MB each.You can also set LTXHWM & LTXEHWM are 80 and 90 > > respectively.We have overcome the long transaction problem here by > > deviating from Informix suggested values of 50 and 60. > > Also , as William suggested, you need to have a look at the code as > > well , as no amount of tuning can help if the code is inefficient. > > Mmmm, put it this way, if YOU were on technical support, and a customer > rang with their system stuck because a long transaction couldn't > rollback, and they had increased LTXHWM & LTXEHWM, would YOU have any > sympathy for them?? > > In my experience, lots of small logs (5-10 Mb) are most useful. If your > granularity is too large, then the effects of LTXHWM & LTXEHWM are > exacerbated. > > Cheers, > -- > Mark. > > +----------------------------------------------------------+-----------+ > | Mark D. Stock mailto:mdstock@mydas.freeserve.co.uk |//////// /| > | http://www.informix.com http://www.informixhandbook.com |///// / file://| > | http://www.iiug.org +-----------------------------------+//// / ///| > | |This email will self-destruct in |/// / ////| > | |10 sec. If you received this email |// / /////| > | |in error, sorry about the mess. |/ ////////| > +----------------------+-----------------------------------+-----------+