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Catalog Cache vs. Buffer Pool for SYSCATSPACE

P: n/a
I understand the concept of catalog cache (memory allocated from the
dbheap to allow catalog lookups without the need to access disk each
time). But the DB2 catalog tablespace (SYSCATSPACE) is assigned a
buffer pool, which seems to perform the same function as catalog
cache.

Is this simply a case of double buffering? Can anyone clear this up?
Nov 12 '05 #1
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P: n/a
Mark wrote:
I understand the concept of catalog cache (memory allocated from the
dbheap to allow catalog lookups without the need to access disk each
time). But the DB2 catalog tablespace (SYSCATSPACE) is assigned a
buffer pool, which seems to perform the same function as catalog
cache.

Is this simply a case of double buffering? Can anyone clear this up?


One thing the catalog cache does but the buffer pool (BP) does not is the
caching of the packed descriptors for various kinds of objects. The packed
descriptors are modeled as BLOBs, and BLOBs don't go through the buffer
pool.

--
Knut Stolze
Information Integration
IBM Germany / University of Jena
Nov 12 '05 #2

P: n/a
Knut Stolze <st****@de.ibm.com> wrote in message news:<cf**********@fsuj29.rz.uni-jena.de>...

One thing the catalog cache does but the buffer pool (BP) does not is the
caching of the packed descriptors for various kinds of objects. The packed
descriptors are modeled as BLOBs, and BLOBs don't go through the buffer
pool.


But the BLOB's, CLOB's themselves still require direct reads from disk, correct?
Nov 12 '05 #3

P: n/a
No, it's the Blobs that are cached. The cache also includes routine
signatures. So DB2, once the cache, is warm will barely touch the
catalog (including the buffer pool) anymore unless things change.

Cheers
Serge
Nov 12 '05 #4

P: n/a
Mark wrote:
Knut Stolze <st****@de.ibm.com> wrote in message
news:<cf**********@fsuj29.rz.uni-jena.de>...

One thing the catalog cache does but the buffer pool (BP) does not is the
caching of the packed descriptors for various kinds of objects. The
packed descriptors are modeled as BLOBs, and BLOBs don't go through the
buffer pool.


But the BLOB's, CLOB's themselves still require direct reads from disk,
correct?


Not if those LOBs are in the catalog cache.

--
Knut Stolze
Information Integration
IBM Germany / University of Jena
Nov 12 '05 #5

P: n/a
Serge Rielau <sr*****@ca.eye-bee-em.com> wrote in message news:<ow*********************@twister01.bloor.is.n et.cable.rogers.com>...
No, it's the Blobs that are cached. The cache also includes routine
signatures. So DB2, once the cache, is warm will barely touch the
catalog (including the buffer pool) anymore unless things change.

Cheers
Serge


The BLOB's, CLOB's are cached in the catalog cache, or are they cached
somewhere else? I am talking about user created BLOB's and CLOB's, not
the ones in the Catalog tables.
Nov 12 '05 #6

P: n/a
Mark wrote:
The BLOB's, CLOB's are cached in the catalog cache, or are they cached
somewhere else? I am talking about user created BLOB's and CLOB's, not
the ones in the Catalog tables.

Ah, regular CLOBs and LOBs are not cached.

Cheers
Serge
Nov 12 '05 #7

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