Logical Logs Size

Forgive me if my question has been discussed recently or repeatedly. I haven't been able to read this newsgroup for ages, but would appreicate your input as I have a limited amount of time to research my questions. Please respond via email if possible, thanks for your help .... Mary Curtis (mary@rez.com) We are running a large OLTP application on a SUN 10000 platform. We have DLTs (jutebox like) tape media. In the past we have always run continuous logging to tape (DAT tape drives). Continuous logging to the DLTs is no longer the preferred method. We plan to run SUN's NetBackup utility to backup the Informix logs when a pre-determined number are full. Our experience has been with running small sized logical logs in our continuous logging environment in the past (2k to 8k in size). At approximately 4k size, our application will fill a log on the system we are discussing in as little as 2 minutes and in as long as 30 minutes given the varying times of the day and the load. The jutebox can't keep up with the logs filling in minutes, the storage media is meant for less often backups, but to stream a lot of information quickly to the tapes. The primary question, HOW BIG TO MAKE THE LOGICAL LOGS? Our system administration group would like to see 50 megabyte logs. That's way too much shared memory for me, or is it?? I'm looking for experience and recommendations on suggested "larger" sized logs. Please also comment on the following concerns if you can: - shared memory (allocating to a bundle to large logs?) - long transactions (increasing the log sizes, have you decreased the long transaction high water marks? We're at 50/60 for LTXHWM/LTXEHWM) - recovery (as long as checkpoints are in line, are you safe? I've been in recovery on a long transaction and hence my concern above about rolling back forever and a day on a long txn) - checkpoints (any special considerations? We currently checkpoint at 150secs, duration usually 0-3 seconds, no complaints) - physical log size (any special considerations when increasing logical log size?) Anything else you think of, please share your experience. Mary Curtis (mary@rez.com) Sr. DBA - Rezsolutins, Inc.