DB2 UDB for z/OS Version 8 Performance Topics - IBM Redbooks

RDS OP POOL (MB) N/A
RID POOL (MB) 0.35
PIPE MANAGER SUB POOL (MB) 0.00
LOCAL DYNAMIC STMT CACHE CNTL BLKS (MB) 3.93
THREAD COPIES OF CACHED SQL STMTS (MB) 29.10
IN USE STORAGE (MB) 16.13
STATEMENTS COUNT 2096
HWM FOR ALLOCATED STATEMENTS (MB) 16.13
STATEMENT COUNT AT HWM 2096
DATE AT HWM 10/23/04
TIME AT HWM 00:59:04.55
BUFFER & DATA MANAGER TRACE TBL (MB) N/A
TOTAL FIXED STORAGE (MB) 0.46
TOTAL GETMAINED STACK STORAGE (MB) 71.28
STORAGE CUSHION (MB) 123.79
DBM1 STORAGE ABOVE 2 GB QUANTITY REAL AND AUXILIARY STORAGE QUANTITY
-------------------------------------------- ------------------ -------------------------------------------- ------------------
FIXED STORAGE (MB) 0.02 REAL STORAGE IN USE (MB) 694.48
GETMAINED STORAGE (MB) 2221.78 AUXILIARY STORAGE IN USE (MB) 0.00
COMPRESSION DICTIONARY (MB) 0.00
CACHED DYNAMIC SQL STATEMENTS (MAX) (MB) 1024.00
DBD CACHE (MAX) (MB) 1024.00
VARIABLE STORAGE (MB) 173.78
VIRTUAL BUFFER POOLS (MB) 468.75
VIRTUAL POOL CONTROL BLOCKS (MB) 0.14
CASTOUT BUFFERS (MB) 0.00
STAR JOIN MEMORY POOL (MB) 0.00
The TOTAL GETMAINED STORAGE has decreased from 599.18 MB in V7 to 236.09 MB in
V8. This is a direct result of buffer pools, buffer pool control blocks, data space lookaside
buffers, castout buffers and compression dictionaries all moving above the bar. We can see
them now recorded in a new area of the report, titled DBM1 STORAGE ABOVE 2 GB. You will
also notice these fields are now marked as N/A under the TOTAL GETMAINED STORAGE
section of the report.
For V8, RID Pool is only referred to RID map, since RID lists have been moved above the bar.
Note that the RDS OP pool is recorded as N/A for V8. In DB2 V7, there was a single RDS OP
pool reported, which all threads use. However in DB2 V8, the RDS OP pool storage for each
thread is allocated from the thread's variable length storage pool. We can see the TOTAL
GETMAINED STACK STORAGE jump from 26 MB to 71 MB. This increase is primarily due to
larger thread-related structures in V8, since they must be larger to accommodate long names.
So, in V8 we see a considerable decrease in TOTAL GETMAINED STORAGE and a
considerable increase in TOTAL GETMAINED STACK STORAGE.
DB2 V8 also breaks down the THREAD COPIES OF CACHED SQL STMTS storage into
more meaningful statistics. Cached SQL statements for dynamic SQL can cause quite a lot of
virtual storage to be consumed.
► THREAD COPIES OF CACHED SQL STMTS reports the virtual storage consumed by
copies of currently executable SQL statements and the executable statements that are
kept beyond commit when KEEPDYNAMIC YES is used.
► IN USE STORAGE reports the amount of virtual storage that is actually allocated to locally
cached dynamic SQL statements, discounting storage not used in the storage allocation
segment.
► STATEMENTS COUNT is the number of locally cached dynamic SQL statements that are
actually using the storage.
The following formula can give you some insight into the degree of fragmentation of storage
which is used to locally cache dynamic SQL statements.
(THREAD COPIES OF CACHED SQL STMTS - IN USE STORAGE) / STATEMENTS COUNT
164 DB2 UDB for z/OS Version 8 Performance Topics