This APAR applies to all platforms under the combination of the
following conditions:
1) A LOCKLIST greater than 8000 pages is used.
2) Many applications are accessing one specific table
concurrently via SELECT or DELETE queries, or via searched
DELETE or CLOSE CURSOR operations against cursor opened FOR READ
ONLY.
If you suspect that you are hitting this problem, collect "db2pd
-latches" at various intervals. The output that is relevant in
this case is column 2 (Holder), column 3 (Waiter) and column 5
(LatchType). If you see many lines of output that have a
LatchType of SQLO_LT_SQLP_LHSH__hshlatch (lock manager hash
table latch) and have the same Holder value (EDU ID of the EDU
holding the latch) with various Waiter values (EDU ID of an EDU
waiting on the latch), then it is possible that you might be
hitting this issue. Note that multiple unique holders may be
present, as is the case in this example.
Address Holder Waiter Filename
LOC LatchType HoldCount
0x07000046EBBE0B58 798762 213934 sqlpLockInternal.h 554
SQLO_LT_SQLP_LHSH__hshlatch 0
0x07000046EBBE0B58 798762 129857 sqlpLockInternal.h 554
SQLO_LT_SQLP_LHSH__hshlatch 0
0x07000046EBBE0B58 798762 140132 sqlpLockInternal.h 554
SQLO_LT_SQLP_LHSH__hshlatch 0
... repeats many times ...
... with the same Holder value ...
... with varying Waiter values ...
0x07000046EBBE0B58 798762 1186579 sqlpLockInternal.h 554
SQLO_LT_SQLP_LHSH__hshlatch 0
0x07000046EBBE0B58 798762 1190691 sqlpLockInternal.h 554
SQLO_LT_SQLP_LHSH__hshlatch 0
0x07000046EBBE0B58 798762 1200514 sqlpLockInternal.h 554
SQLO_LT_SQLP_LHSH__hshlatch 0
0x07000046EBBE0B58 798762 1202054 sqlpLockInternal.h 554
SQLO_LT_SQLP_LHSH__hshlatch 0
0x07000046EBBE0B58 798762 800313 sqlpLockInternal.h 554
SQLO_LT_SQLP_LHSH__hshlatch 0
0x07000046EBBE0B58 798762 467072 sqlpLockInternal.h 554
SQLO_LT_SQLP_LHSH__hshlatch 0
... skip some other entries ...
0x07000046EBBE0B58 1156509 213934 sqlpLockInternal.h 520
SQLO_LT_SQLP_LHSH__hshlatch 1
0x07000046EBBE0B58 1156509 129857 sqlpLockInternal.h 520
SQLO_LT_SQLP_LHSH__hshlatch 1
0x07000046EBBE0B58 1156509 140132 sqlpLockInternal.h 520
SQLO_LT_SQLP_LHSH__hshlatch 1
... repeats many times ...
... with the same Holder value (but different than the Holder
value above) ...
... with varying Waiter values ...
0x07000046EBBE0B58 1156509 148094 sqlpLockInternal.h 520
SQLO_LT_SQLP_LHSH__hshlatch 1
0x07000046EBBE0B58 1156509 149379 sqlpLockInternal.h 520
SQLO_LT_SQLP_LHSH__hshlatch 1
0x07000046EBBE0B58 1156509 160167 sqlpLockInternal.h 520
SQLO_LT_SQLP_LHSH__hshlatch 1
... skip other entries ...
Once you have confirmed from "db2pd -latches" output that your
environment might be suffering from this issue, you can collect
additional information from agents to confirm that this specific
problem is the issue in your environment.
For each of the holder values in the "db2pd -latches" output,
collect "db2pd -stacks <holder_EDU_ID>" to dump the stack trace
of the EDUs waiting on the hash latch. This may need to be
collected mutiple times in order to capture an instance when the
EDU is actively holding the latch.
The holder EDU stack that indicates the problem scenario looks
like this:
-------Frame------ ------Function + Offset------
0x0900000045849C34 getConflictComplex__17SQLO_SLATCH_CAS64FCUl +
0x3D4
0x090000004584A258 getConflict__17SQLO_SLATCH_CAS64FCUl + 0xD8
0x0900000045EEA990 sqlplrl__FP9sqeBsuEduP14SQLP_LOCK_INFO +
0x3F0
0x090000004685F3A0 sqldmclo__FP8sqeAgentPP8SQLD_CCBi + 0x1BA0
0x09000000468545F0 sqlriclo__FP8sqlrr_cbP9sqlri_taoi + 0x550
0x0900000045B9BA98 sqlricjp__FP8sqlrr_cbP12sqlri_opparmilT4 +
0x2B8
0x0900000045B9B4C8 sqlricls_simple__FP8sqlrr_cbil + 0x1488
0x09000000476F15AC sqlrr_process_close_request__FP8sqlrr_cbiN32
+ 0x20C
0x0900000046EFEEE8
sqlrr_close__FP14db2UCinterfaceP15db2UCCursorInfo + 0x208
In addition, for various waiter values in the "db2pd -latches"
output, collect "db2pd -stacks <waiter_EDU_ID>". Again, you may
need to collect this multiple times in order to capture an
instance when the EDU is actively waiting on the latch.
The waiter EDU stack that indicates the problem scenario looks
like this:
-------Frame------ ------Function + Offset------
0x0900000045849C34 getConflictComplex__17SQLO_SLATCH_CAS64FCUl +
0x3D4
0x090000004584A258 getConflict__17SQLO_SLATCH_CAS64FCUl + 0xD8
0x090000004608EA20 sqlplrq__FP9sqeBsuEduP14SQLP_LOCK_INFO +
0x1EA0
0x09000000460D8CF4
sqldLockTable__FP8sqeAgentP14SQLP_LOCK_INFOUiUsi + 0x114
0x09000000468CE908
sqldScanOpen__FP8sqeAgentP14SQLD_SCANINFO1P14SQLD_SCANINFO2PPv +
0xB28
0x0900000046856E30 sqlriopn__FP8sqlrr_cbP9sqlri_taoPi + 0x1550
0x09000000477C4918 sqlrita__FP8sqlrr_cb + 0xC78
0x09000000468F7278 sqlriSectInvoke__FP8sqlrr_cbP12sqlri_opparm +
0x3F8
0x0900000046EF5908
sqlrr_process_fetch_request__FP14db2UCinterface + 0xC48
0x0900000046EF7228
sqlrr_open__FP14db2UCinterfaceP15db2UCCursorInfo + 0xE08
If the primary conditions are met, and holder EDU and
waiter EDU stacks match those listed above, then you might
obtain relief after applying the local fix or by upgrading to a
newer level of DB2 that contains the fix for this APAR.
Local Fix
Apply the following registry setting and restart DB2.
DB2_KEEPTABLELOCK=TRANSACTION |
