Total Virtual Pool Size1

Leslie Pendlebury-Bowe

Total Virtual Pool Size1
me again .. give me an hour and I will post the details to here ..

Leslie


______________________________ Reply Separator _________________________________
Subject: Total Virtual Pool Size
Author: Andy Hunt <[login to unmask email]> at Internet
Date: 12/14/99 3:24 PM


How big are your Virtual Pools ?

Ive heard from an IBM source that problems can occur if you allocate > 500-600
Mb total and that it is recommended total virtual pool allocation is below this
(futher expansion should use hiperpools). Ive trawled through the DB2 Storage
Informational APARs II04309(II10817) but cant find anything that indicates this
problem/strategy.

Does anybody have total virtual pool allocation > 500-600Mb ? If so, whats their
size and have you experienced any problems (at V5 or V6)?
Has anybody seen an APAR containing this recommendation ?

Kind Regards,
Andy Hunt - Scottish And Southern Energy


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Isaac Yassin

Re: Total Virtual Pool Size
(in response to Leslie Pendlebury-Bowe)
Hi,
I'm on 350Mb-400MB for VBP. 32MB EDM. Don't remember the other.
--
Isaac Yassin

DBMS & IT Consultant

Tel: +972 9 9505172
Cel: +972 54 452793
Fax: +972 9 9560803



Jim Lewandowski

Re: Total Virtual Pool Size
(in response to Leslie Pendlebury-Bowe)
Very interesting question.

We have the full 1.6G virtual, and another 1.5G or so if Hiperpool
buffers.

I suppose that having a smaller virtual with larger hiperpool will save
the CPU of having to have MVS move the virtual buffer (addressable by
MVS and mapped by some real storage at that instant) out to expanded
storage (only page addressable by MVS) via the hiperpool buffer. In
other words, hiperpool buffers have to be moved to a virtual bufferpool
page to be accessed.

However, the 75 microsecond CPU it takes to synchronously move a page
to/from real to estore probably won't be easily measured/quantified.
You could possibly save a lot of the real/virtual buffer to
expanded/hiperpool buffer moves.

It IS a good point though about virtual/hiperpool splitting.

Jim Lewandowski



Leslie Pendlebury-Bowe

Re: Total Virtual Pool Size1
(in response to John Rosser)
I am still working on my "very" long mail detailing how you calculate
your Virtual Pool storage ..

more to come soon ..

Les


______________________________ Reply Separator _________________________________
Subject: Re: Total Virtual Pool Size1
Author: John Rosser <[login to unmask email]> at Internet
Date: 12/15/99 8:03 AM


Currently allocated nearly 900 Mb of virtual buffer pool storage in both
members of a data sharing group. Nervous? Sure I am, but not all buffers
are being used concurrently.
We are splitting applications into their own DB2s to prove to the app
support group, some of their code ...(well, you probably know what I mean).
Plenty of work, but will be easier to tune.
Other items of interest besides actual virtual buffer pool values in the
DBM1 address space:
1)EDM Pool Size
2)RID Pool Size
3)some DB2 code
4)Control blocks for # of open datasets, virtual & hiper pools, CTHREAD,
DDF threads, RDS pool, and compression dictionaries.

PQ24852 used to state recommendations of using 500Mb or less for virutal
buffer pools, but that has since been taken out.
Regards,
John Rosser
Duke Energy Corporation








John Rosser

Re: Total Virtual Pool Size1
(in response to Isaac Yassin)
Currently allocated nearly 900 Mb of virtual buffer pool storage in both
members of a data sharing group. Nervous? Sure I am, but not all buffers
are being used concurrently.
We are splitting applications into their own DB2s to prove to the app
support group, some of their code ...(well, you probably know what I mean).
Plenty of work, but will be easier to tune.
Other items of interest besides actual virtual buffer pool values in the
DBM1 address space:
1)EDM Pool Size
2)RID Pool Size
3)some DB2 code
4)Control blocks for # of open datasets, virtual & hiper pools, CTHREAD,
DDF threads, RDS pool, and compression dictionaries.

PQ24852 used to state recommendations of using 500Mb or less for virutal
buffer pools, but that has since been taken out.
Regards,
John Rosser
Duke Energy Corporation