Informix

Amit:

You need to check the BTR3 metric for each of your buffer caches (2K & 12K). If either is over 6 turns/hour then you should add more buffers. If not, then the number of buffers is not an issue. The easiest way to do this? Go to my web site and download the ratios.shr_ak package, install the ratios.sql stored procedure, then you can run the newratios.ksh script to calculate and produce the metrics report that includes the BTR3 calculations.

Art

Amit:

I just noticed that you increased the "default" bufferpool setting. That setting is ONLY used to create a new bufferpool for a new page size if a new dbspace with a new page size is created dynamically without having created the bufferpool first (using the API function). You would have had to increase the 12K bufferpool.

Art

You probably intended to increase your 12k bufferpool rather than the default, unless you have dbspaces with pages sizes that are not already listed with their own bufferpool entry, e.g. 2k and 12k, otherwise this won't change anything meaningful.  The number of buffers that you have assigned seems very low compared to the 12k.  Definitely try Art's BTR ratios to see the turnover.  I expect you will see some high numbers.  Also take a look at onstat -g buf and check the caching for reads and writes.

The suggestion of disabling flow control is a good one.  Check onstat -g rss verbose and the last 2 rows to see if the number of delays and time of last delay shows anything other than 0 and blank.  If so, it indicates that the rss has fallen behind and is throttling the primary server.  The default for flow control is enabled and not at a very big value.  Increasing the flow control limit or disabling flow control for now may reduce any of those delays.  The resources on the RSS are very low compared to the primary and hdr so it may well struggle to keep up when under heavy load, and that will slow the primary down. 

Dear Art & Mike, 

            So as I changed the default BUFFERPOOL instead of 2K or 12K BUFER Size BUFFERPOOL, so will it impact, if I keep the Default BUUFERPOOL size 4000, and don't change anything for rest BUFFERPOOL values. So will it impact something on the Primary/HDR/RSS replication or can it lead to any other performance issue?

Thanks

Amit Patel

Amit:

No. The "default" bufferpool setting, as I already noted, ONLY takes effect if you create a new dbspace that has a page size that is not 2K or 12K. If, for example, you were to create a new 16K dbspace in order to move some big indexes into it, and do not use the API function "add bufferpool" or the onparams utility with the options "-b -g <pagesize>" without the "-n <# pages>" option, then the "default" entry would be used to determine the number of pages to create in the new 16K bufferpool and how to configure the other options it specifies. Otherwise, the "default" BUFFERPOOL entry does nothing at all.

Art