High Memory Allocations of type KGNFS in Shared Pool (Doc ID 1309337.1)

Last updated on DECEMBER 15, 2011

Applies to:

Oracle Server - Enterprise Edition - Version: 11.1.0.7 to 11.2.0.2 - Release: 11.1 to 11.2
Information in this document applies to any platform.

Symptoms

You may see high memory allocations in the shared pool of type
"kgnfs rserver", "kgnfs local" and "kgnfs path".

If these allocations grow large enough they may cause ORA-04031 error.

- ORA-04031: unable to allocate 592 bytes of shared memory ("shared pool","unknown object","sga heap(1,0)","kgnfs local")
- ORA-00600: internal error code, arguments: [kmgs_parameter_update_timeout_1], [4031], [], [], [], [], [], [], [], [], [], []
- ORA-04031: unable to allocate 1456 bytes of shared memory ("shared pool","unknown object","sga heap(1,0)","kgnfs rserver")

The incident trace file shows the following failing statement:
----- Current SQL Statement for this session (sql_id=dnk8dw55sjz3h) -----
SELECT value FROM v$spparameter WHERE name = 'log_archive_min_succeed_dest'  AND sid='*'


The ORA-4031 trace file shows high values for kgnfs memory allocations:

==============================
Memory Utilization of Subpool 1
================================
Allocation Name Size
_________________________ __________
..............
"sql area " 139312592
"kgnfs rserver " 373405552
...............
"kgnfs local " -1945451456 <== (A negative value like this is due to an internal overflow error and indicates value over 2G)

Changes

- Direct NFS is enabled.

- For each "kgnfs rserver" entry also entries of type "kgnfs path" and "kgnfs local" are allocated, so these go hand in hand.

- The call stack of the failure show we are opening the spfile:
Call stack:  kghalp <- kgnfsallocmem <- kgnfs_create_rserver_ent <- kgnfsgetmnthdl <- kgodm_getnfscdata <- kgodm_identify <- odm_identify
<- ksfd_odmopn <- ksfdopn<- kspifisp <- ksp_spfile_open<- ksp_spfile_get <- kspspfftcb <- qerfxFetch <- opifch2

- The access of the spfile looks the result of accessing the v$parameter view.

- To monitor the size of sub pools related to kgnfs use the select statements:

select sum(bytes) from v$sgastat where name like '%nfs%';
select pool, name, bytes from v$sgastat where pool like '%shared%' and name like '%nfs%';


Cause

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