**please note my email address change**
The short answer is that there isn’t much connection between
z/OS Pages and DB2 pages. A DB2 page is an image of a data page
from a VSAM LDS which is (part of) the DB2 pageset. It may have
updates written to it, and those updates may or may not yet be
reflected to the underlying LDS.
A DB2 Page is read into, or “externalized” from
(written back to its underlying dataset on DASD), a DB2 Bufferpool
(and potentially GroupBufferPool, for parallel-sysplex
A DB2 Bufferpool is one or more z/OS PAGEs, with page size
determined (I think) by DB2 subsystem parameters. DB2 Bufferpools
can be paged, or can be un-page-able, again depending on DB2
subsystem parameters, but are always (a) z/OS Page(s).
So: A DB2 Page contains data, and is transiently in a z/OS Page.
But there isn’t any connection between them which isn’t
mediated by the DB2 subsystem (Bufferpool Manager).
Hope that helps, and of course, I’d welcome corrections from
other List-ers on matters of fact in the above.
Computer Systems Manager
5 Manhattan West (33rd St at 10th Ave)
New York, NY 10001-2632
[cid:[login to unmask email]
From: Tushar Jha [mailto:[login to unmask email]
Sent: Monday, September 25, 2017 11:41 AM
To: [login to unmask email]
Subject: [DB2-L] - co-relation between DB2 PAGE and z/OS PAGE
I have a question which might be very basic in nature.I have
searched the net ( not extensively ) , but have not got any
How are DB2 PAGES related to z/OS PAGES,FRAMES,SLOTS?
DB2 internally stores tablespaces and indexes in PAGEs of different
In z/OS , A block of central storage is called a FRAME, a block of
auxiliary storage (DASD) is called a SLOT, and a block of virtual
storage is called a PAGE.So, PAGEs in z/OS are there to support
* When a DB2 PAGE is first brought in from DASD , it is brought
into its designated Buffer Pool which is allocated inside the DBM1
address space of DB2, all of this obviously is happening inside
z/OS.So, when the page is brought into buffer pool, where does z/OS
( or to be more precise its PAGING, virtual addressing ) comes into
place. And when the DB2 PAGE is brought into buffer pool, is that
really a z/OS PAGE or a portion of z/OS PAGE. As far as I know,
z/OS only supports 4KB and 1MB PAGE sizes ( will be happy to stand
corrected ). DB2 has PAGE sizes of 4KB, 8KB, 16KB and 32KB. So, how
does DB2 PAGE fit into z/OS page.
Is DB2 doing this behind the scenes or there is no relation at
* Also, how does this work, when DB2 PAGEs are written back to DASD
* How does DB2 PAGE relate to SLOTS ( block of z/OS storage on DASD
) since PAGES in DB2 are called PAGES even when they are in
* Does z/OS paging play any role in the way DB2 divides its
tablespace/index into PAGEs
This probably doesn’t affect my day to day work, and some of
this probably has more to do with z/OS intricacies.
I would be very grateful, if you can shed some insights on this or
point me to any documentation which would help me understand
Thanks in advance,
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