Re: No blocking session for wait event: 'Library cache pin'

On Tue, Aug 2, 2011 at 11:19 AM, Sanjeev M <sanjeevorcle_at_gmail.com> wrote:

> Environment: 2 node RAC on OEL 5
> Grid Home : 11.2.0.2
> RDBMS Home: 11.1.0.7.7
>
> On our database, Session was waiting most of the time on 'library cache
> pin' wait - for a decent amount like a minute or more before toggling to
> another wait event db file sequential read and back to this wait.
>
> Could it be a bug that the blocker session is not showing up?
>
> select p1raw,p1text,event,sid from v$session where sid=1710;
> P1RAW
> P1TEXT
> EVENT SID
> ----------------
> ----------------------------------------------------------------
> ---------------------------------------------------------------- ----------
> 0000000356213B10 handle
> address library cache
> pin 1710
> select * from x$kglpn where KGLPNHDL='0000000356213B10';
> no rows selected <=== Expected to see some info here regading object,
> lock mode (Either null/shared or exclusive) however no output!!!
>
> Also checked for other handle addresses from gv$session to see if it
> possibly is having some kind of dependancy:
>
> select inst_id,p1raw,count(1) from gv$session where event='library cache
> pin' group by inst_id,p1raw;
> INST_ID P1RAW COUNT(1)
> ---------- ---------------- ----------
> 1 000000032FA9B7A0 1
> 1 0000000356213B10 1
>
> select * from x$kglpn where KGLPNHDL='000000032FA9B7A0';
> no rows selected <=== Expected to see some info here regading object,
> lock mode (Either null/shared or exclusive) however no output!!!
> Also tried gv$ges_blocking_enqueue however output does not show anything
> related to *"lib pin -- Nx Gx"*
>
> 'WAI INST_ID SPID RESOURCE_NAME1
> ---- ---------- ---------- ------------------------------
> Wait 1 10838 [0x75daf18b][0x4c05b769],[NB]
> Wait 2 17532 [0x19][0x2],[RS]
> Wait 2 0 [0x8c0][0x10000],[BL]
> Blkr 1 10132 [0x19][0x2],[RS]
> Blkr 2 17508 [0x1][0x0],[PW]
>
> Ran tanel poder's snapper while this was happening and it says session on
> CPU:
>
> _at_snapper ash=sql_id+event+wait_class+p1+p2+p3 5 1 1710
> Sampling SID 1710 with interval 5 seconds, taking 1 snapshots...
> -- Session Snapper v3.14 by Tanel Poder _at_ E2SN ( http://tech.e2sn.com )
>
>
> --------------------------------------------------------------------------------------------------------------------------------
> Active% | SQL_ID | EVENT | WAIT_CLASS |
> P1 | P2 | P3
>
> --------------------------------------------------------------------------------------------------------------------------------
> * 100% | 10za9fj1va0kd | ON CPU | ON CPU
> | | |*
> -- End of ASH snap 1, end=2011-08-02 11:00:58, seconds=5, samples_taken=42
>
> PL/SQL procedure successfully completed.
>
> *SQL statement that was being run for this session was:*
>
> select msi.inventory_item_id from mtl_parameters mp,
> mtl_system_items msi,
> mtl_system_items_interface msii where
> msii.transaction_id = :transaction_id_bind and
> msii.set_process_id = :set_id_bind2 *and rownum = 1
> * and msi.organization_id = mp.organization_id
> and msi.segment1 = msii.segment1
> Plan hash value: 904999408
>
> ----------------------------------------------------------------------------------------------------------------
> | Id | Operation | Name |
> Rows | Bytes | Cost (%CPU)| Time |
>
> ----------------------------------------------------------------------------------------------------------------
> | 0 | SELECT STATEMENT |
> | | | 342 (100)| |
> |* 1 | COUNT STOPKEY |
> | | | | |
> | 2 | NESTED LOOPS | |
> 21 | 882 | 342 (1)| 00:00:05 |
> | 3 | NESTED LOOPS | |
> 21 | 798 | 342 (1)| 00:00:05 |
> | 4 | TABLE ACCESS FULL | MTL_SYSTEM_ITEMS_B |
> 12245 | 191K| 342 (1)| 00:00:05 |
> |* 5 | TABLE ACCESS BY INDEX ROWID| MTL_SYSTEM_ITEMS_INTERFACE
> | 1 | 22 | 0 (0)| |
> |* 6 | INDEX RANGE SCAN | MTL_SYSTEM_ITEMS_INTERFACE_N6
> | 1 | | 0 (0)| |
> |* 7 | INDEX UNIQUE SCAN | MTL_PARAMETERS_U1
> | 1 | 4 | 0 (0)| |
>
> ----------------------------------------------------------------------------------------------------------------
> Predicate Information (identified by operation id):
> ---------------------------------------------------
> 1 - filter(ROWNUM=1)
> 5 - filter(("MSII"."SET_PROCESS_ID"=:SET_ID_BIND2 AND
> "MSI"."SEGMENT1"="MSII"."SEGMENT1"))
> 6 - access("MSII"."TRANSACTION_ID"=:TRANSACTION_ID_BIND)
> 7 - access("MSI"."ORGANIZATION_ID"="MP"."ORGANIZATION_ID")
> Any pointers or help much appreciated.
>
> Thanks,
> Sanjeev.
>

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