False increase of 'Global Cache Blocks Lost' or 'gc blocks lost' after upgrade to 12c (Doc ID 2096299.1)

Last updated on JUNE 13, 2017

Applies to:

Oracle Database - Enterprise Edition - Version 12.1.0.2 to 12.1.0.2 [Release 12.1]
Information in this document applies to any platform.

Symptoms

'gc blocks lost' increases after 12c Upgrade, we can see:


1. Statistic increases constantly:

 

SELECT A.INST_ID "INSTANCE", A.VALUE "GC BLOCKS LOST",
B.VALUE "GC CUR BLOCKS SERVED",
C.VALUE "GC CR BLOCKS SERVED",
A.VALUE/(B.VALUE+C.VALUE) RATIO
FROM GV$SYSSTAT A, GV$SYSSTAT B, GV$SYSSTAT C
WHERE A.NAME='gc blocks lost' AND
        B.NAME='gc current blocks served' AND
        C.NAME='gc cr blocks served' and
        B.INST_ID=a.inst_id AND
        C.INST_ID = a.inst_id
/

<< 12.1.0.2>

11:02:14 SQL> /

  INSTANCE GC BLOCKS LOST GC CUR BLOCKS SERVED GC CR BLOCKS SERVED      RATIO
---------- -------------- -------------------- ------------------- ----------
         1            573                79063               36031 .004978539
         2            337                36154               63131 .003394269


11:07:03 SQL> /

  INSTANCE GC BLOCKS LOST GC CUR BLOCKS SERVED GC CR BLOCKS SERVED      RATIO
---------- -------------- -------------------- ------------------- ----------
         1            573                79084               36112 .004974131
         2            338                36176               63181 .003401874

<< 11.2.0.3>>

11:02:52 SQL> /

  INSTANCE GC BLOCKS LOST GC CUR BLOCKS SERVED GC CR BLOCKS SERVED      RATIO
---------- -------------- -------------------- ------------------- ----------
         1              0                 7687                  49          0
         2              0                   34                  33          0

11:07:13 SQL> /

  INSTANCE GC BLOCKS LOST GC CUR BLOCKS SERVED GC CR BLOCKS SERVED      RATIO
---------- -------------- -------------------- ------------------- ----------
         2              0                   36                  55          0
         1              0                 7696                  49          0

 

2. If EM is used you may see alerts produced like:

Host=node1
Target type=Database Instance
Target name=<target name>
Categories=Error
Message=Metrics Global Cache Blocks Lost is at 4
Severity=Warning
Event reported time=Apr 2, 2015 2:50:27 AM CDT
Operating System=Linux
Platform=x86_64
Associated Incident Id=298857
Associated Incident Status=New
Associated Incident Owner=
Associated Incident Acknowledged By Owner=No
Associated Incident Priority=None
Associated Incident Escalation Level=0
Event Type=Metric Alert
Event name=rac_global_cache:lost
Metric Group=Global Cache Statistics
Metric=Global Cache Blocks Lost
Metric value=4
Key Value=
Rule Name=Database Availability and Critical States <DBA_owner>,Metric Alerts
Event Rule
Rule Owner=<DBA_owner>
Update Details:
Metrics Global Cache Blocks Lost is at 4

 

 

Changes

 Customer upgrade from 11.2.0.3 to 12.1.0.2

Cause

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