RE: tuning log buffers

SAP provides the following guidelines to their customers: o PHYSBUFF Installed value: 1024 This parameter determines the size of the two buffers in which the physical logs will be stored temporarily. With the command `onstat -l`, you can check whether the set size is sufficient for your system. The value "pages/io" should be at least 75% of the value "bufsize". Oherwise, you should change the parameter PHYSBUFF and watch the change of the "pages/io" output. Example: Physical logging Buffer bufused bufsize numpages numwrits pages/io P-2 759 768 276464 371 745.19 phybegin physize phypos phyused %used 200035 220000 117989 47149 21.43 If the ratio between "pages/io" and "bufsize" is less than 75%, you should decrease the value for PHYSBUFF. If the ratio between "pages/io" and "bufsize" is more than 75%, you should increase the value for PHYSBUFF. o LOGBUFF Installed value: 32 This parameter determines the size of the three buffers into which the logical logs will store temporarily. With the command `onstat -l`, you can check whether the set size is sufficient for your system. The value "pages/io" should be at least 75% of the value "bufsize". Oherwise, you should change the parameter LOGBUFF and watch the change of the "pages/io" output. Example: Logical logging Buffer bufused bufsize numrecs numpages numwrits recs/pages pages/io L-1 0 8 5898609 898878 358944 6.6 2.5 If you use a logical volume manager with disk stripping (LVM), you can optimize performance by adapting the buffer size to the strip size. This is the exception of the guideline described above. If the ratio between "pages/io" and "bufsize" is less than 75%, you should decrease the value for LOGBUFF. If the ratio between "pages/io" and "bufsize" is more than 75%, you should increase the value for LOGBUFF. -----Original Message----- From: Top Cat [mailto:cstefanick@ocsmgmt.com] Sent: Tuesday, January 11, 2000 1:22 PM To: informix-list@iiug.org Subject: tuning log buffers What I know: You control the size of the log buffers through the onconfig variables LOGBUFF (logical) and PHYSBUFF (physical). By increasing their size you trade safety for speed. What I don't know: How do you know if these variables need to be increased/decreased to optimize performance? Are their any good onstat commands or anything else I should look at? Any help would be appreciated!