Discussion created by ca.portal.admin on Oct 13, 2009
Hello All:

Does anyone out there have an XA REENTRANT PROGRAM POOL defined larger than=
32760? If so how large have you made it and has it caused any repercussion=
s on the Operating System?

Bill Allen

(704) 641-0296
IDMS 3rd-party providers forum


"I didn't see a lot of replies to this query - so I thought I'd provide the following feedback - for what it's worth?

As you can see from the following display our XA Reentrant Pool is 66,867,200 bytes ( approx 67 Mb) and we have no problems. How did we pick the size? At most sites I've worked at I run a Load Module Size report against the application DDLDCLOD area to total the size of all Maps, Dialogs, Subschemas and Tables. I then add this to the amount of pool used immediately after startup and use that value as my pool size.

With this approach my ""Loads into unallocated space"" is very close to 100% - ""Loads overlaying program not in use"" is thus very close to 0%. My ""Pages in pool"" and ""Pages loaded"" are almost the same under these conditions.

Prior to this action I have seen sites with ""Pages loaded"" of 5, 10, 50 times or more than ""Pages in pool"". This of course means a lot of needless I/O to DDLDCLOD. After the changes I have seen PMRM show I/O against DDLDCLOD drop from top 5 to 10 hit areas - right down to the bottom. This frees up much needed I/O bandwidth for application databases.

That I can't achieve this as shown in the figures below (for my current site) is due to a few things: 1) our single DB/DC region supports 3 complete businesses, each of which has its own suite of applications, 2) the applications in use change at shift changes and as we move from day shift to night shift in each agency, 3) to use the approach of making the XA RE Pool large enough to hold all the applications for all the agencies would likely cause our system paging rates to go through the roof.

Our trade off to causing system wide paging problems is to allow our XA RE pool to reload itself about 5-10 times a day - this is a relatively smooth process spread across the entire day as the agency/application usage profile changes - so we don't get a really heavy hit on DDLDCLOD all day long.

Hopefully this allays any fears of horrible consequences of large program pool sizes, and also provides some insight into a couple of approaches to a XA RE Program pool sizing exercise.

HTH - cheers - Gary

d ac xa re prog pool
*** Display of XA Reentrant Pool ***
Pages in pool 130600
Bytes in pool 66867200
Loads to pool 19832
Pages loaded 1389188
Load conflicts 0

Pages allocated 30575 100% of pool
Pages in use by one program 5925 5% of pool
Pages in use by multiple programs 0 0% of pool
High-Water mark of pages allocated 30600 100% of pool
Loads into unallocated space 4167 21% of loads
Loads overlaying program not in use 15665 79% of loads
Loads overlaying program in use 0 0% of loads

Gary Cherlet
Justice Technology Services
Department of Justice, SA Government

"""""""" Telephone +61 (0)8 8226 5199
@@ Facsimile +61 (0)8 8226 5311
> Mobile +61 (0)41 333 1613

On this page I appear to be deeply concerned about one thing or another ....... this is merely an old habit of the face Leonard Cohen

This e-mail message and any attachments are qualified as follows: Addressing: If you have received this e-mail in error, please advise by reply e-mail to the sender. Please also destroy the original transmission and its contents. Confidentiality: This e-mail may contain confidential information which also may be legally privileged. Only the intended recipient(s) may access, use, distribute or copy this e-mail. Individual Views: Unless otherwise indicated, the views expressed are those of the sender, not Justice Technology Services. Computer Viruses: It is the recipient's responsibility to check the e-mail and any attached files for viruses.