IFCID 001 - QVLS Data
This topic shows detailed information about "Record Trace - IFCID 001 - QVLS Data".
The QVLS latch counters represent the number of suspends that were performed by agents that attempted to obtain a latch.
The DB2 latch contentions can be traced by running a
performance trace for IFCID 51, 52, 56, and 57.
The latch class counters may represent more than one contention
because they are reported as modulo 32.
For example, LC12 could be either due to latch class
X'0C'
or latch class X'4C'.
The following paragraph shows the predominant latch contention
for each latch class.
The latch class contentions per second are
reported in the Statistics report and trace.
If the latch class contentions per second are:
- Less than 1000, you can ignore them.
- Between 1000 and 10000, you need to start monitoring the issue.
- Greater than 10000 and if this has an impact on your performance, gather the performance trace for the IFCIDs 51,52,56,and 57. Then contact IBM support for assistance.
There is not a one-to-one relationship between the QVLS counters and IFCID 56 or 57, because an agent might suspend multiple times or not at all, while trying to obtain a latch. That is why the QVLS counters are not directly related to Accounting Class 3.
Record trace - IFCID 001 - QVLS Data
The field labels shown in the following sample layout of "Record Trace - IFCID 001 - QVLS Data" are described in the following section.
QVLS DATA
QVLSLC01 0 QVLSLC02 0 QVLSLC03 0 QVLSLC04 0 QVLSLC05 0 QVLSLC06 0
QVLSLC07 0 QVLSLC08 0 QVLSLC09 0 QVLSLC10 8 QVLSLC11 0 QVLSLC12 0
QVLSLC13 0 QVLSLC14 58 QVLSLC15 0 QVLSLC16 0 QVLSLC17 0 QVLSLC18 0
QVLSLC19 3 QVLSLC20 0 QVLSLC21 6 QVLSLC22 0 QVLSLC23 1907 QVLSLC24 131
QVLSLC25 0 QVLSLC26 0 QVLSLC27 19 QVLSLC28 0 QVLSLC29 3 QVLSLC30 25
QVLSLC31 4 QVLSLC32 147 QVLSLC254 0- QVLSLC01
This field is infrequently used.
Field Name: QVLSLC01
- QVLSLC02
The predominant latch usage is: Global authorization cache.
Field Name: QVLSLC02
- QVLSLC03
The predominant latch usage is: DDF disconnect.
Field Name: QVLSLC03
- QVLSLC04
- The predominant latch usage is: SYSSTRING cache.
Field Name: QVLSLC04
- QVLSLC05
The predominant latch usage is: IRLM data sharing exits or RLF.
Field Name: QVLSLC05
- QVLSLC06
The predominant latch usage is: Data sharing index split.
Field Name: QVLSLC06
- QVLSLC07
The predominant latch usage is: Index lotch and OBD allocation.
Field Name: QVLSLC07
- QVLSLC08
The predominant latch usage is: Query parallelism.
Field Name: QVLSLC08
- QVLSLC09
The predominant latch usage is: Utilities or stored procedure URIDs.
Field Name: QVLSLC09
- QVLSLC10
- The predominant latch usage is for Sequence objects
(stand-alone and
table-based Identity Column).
DB2 12 latch contention can be significantly reduced
for the Identity Column in a data-sharing environment because of the
reduction in log force write.
Field Name: QVLSLC10
- QVLSLC11
- The predominant latch usage is for Sequence objects
(stand-alone and table-based Identity Column) for
concurrent transactions. DB2 12
latch contention can be significantly reduced
for the Identity Column in a data-sharing environment
because of the reduction in log force write.
Field Name: QVLSLC11
- QVLSLC12
- The predominant latch usage is
database allocation control latch (latch class X'0C')
or WebSphere® global
transaction ID latch (latch class X'4C').
Field Name: QVLSLC12
- QVLSLC13
The predominant latch usage is: Pageset operations.
Field Name: QVLSLC13
- QVLSLC14
- The predominant latch usage is represented by various
buffer pool related activities,
including buffer pool control block and pool serialization.
Field Name: QVLSLC14
- QVLSLC15
The predominant latch usage is: ARCHIVE LOG MODE(QUIESCE).
Field Name: QVLSLC15
- QVLSLC16
- The predominant latch usage is: UR synonym chain.
Field Name: QVLSLC16
- QVLSLC17
The predominant latch usage is: RURE chain.
Field Name: QVLSLC17
- QVLSLC18
The predominant latch usage is: DDF resynch list.
Field Name: QVLSLC18
- QVLSLC19
- The predominant latch usage is logical log write
(in contrast to physical log write).
Field Name: QVLSLC19
- QVLSLC20
The predominant latch usage is: System checkpoint.
Field Name: QVLSLC20
- QVLSLC21
The predominant latch usage is: Accounting rollup.
Field Name: QVLSLC21
- QVLSLC22
The predominant latch usage is: Internal checkpoint.
Field Name: QVLSLC22
- QVLSLC23
- The predominant latch usage is Buffer Manager latch for
page latch contention timer queue or deferred write latch.
Both types of latches have latch class X'17'.
Field Name: QVLSLC23
- QVLSLC24
- The predominant latch usage is
EDM LRU latch or Buffer Manager prefetch scheduling latch.
EDM LRU latch can be identified by latch class X'18'
while Buffer Manager prefetch scheduling latch can be
identified by latch class X'38' in a latch
contention trace.
Field Name: QVLSLC24
- QVLSLC25
- The predominant latch usage is: EDM hash latch.
Field Name: QVLSLC25
- QVLSLC26
The predominant latch usage is: Dynamic statement cache.
Field Name: QVLSLC26
- QVLSLC27
- The predominant latch usage is: stored procedure
queue latch and UDF.
Field Name: QVLSLC27
- QVLSLC28
The predominant latch usage is: Stored procedures or authorization cache.
Field Name: QVLSLC28
- QVLSLC29
The predominant latch usage is: Field procs and DDF transaction manager.
Field Name: QVLSLC29
- QVLSLC30
The predominant latch usage is: Agent services.
Field Name: QVLSLC30
- QVLSLC31
The predominant latch usage is: Storage manager.
Field Name: QVLSLC31
- QVLSLC32
- The predominant latch usage is
shared storage pool latch.
Field Name: QVLSLC32
- QVLSLC254
The predominant latch usage is: Index latch.
Field Name: QVLSLC254