Instance Hangs or Crashes as LMS Waits for latch 'gc element' Held by DIAG Process (Doc ID 1348264.1)

Last updated on FEBRUARY 08, 2019

Applies to:

Symptoms

If DIAG process holds latch "gc element" and dumps system state, if can block LMS from getting the latch and cause instance to hang or crash:

• Instance alert.log

LMS1 (ospid: 31959) waits for latch 'gc element' for 49 secs.
..
ORA-29771: process DIAG (OSID 31937) blocks LMS1 (OSID 31959) for more than 70 seconds
..
DIAG (ospid: 31937) is hanging without a blocker.
LMHB (ospid: 31965) kills DIAG (ospid: 31937).
..
 
OR


LMS0 (ospid: 25991) waits for latch 'gc element' for 8 secs.
..
ORA-29770: global enqueue process LMS0 (OSID 25991) is hung for more than 140 seconds
..
LMHB (ospid: 26001): terminating the instance due to error 29770
..
opiodr aborting process unknown ospid (26195) as a result of ORA-1092

• Short stack dump

diag process:

..__sighandler write sdbgrfwf_write_file .. kcldle kclbsy ksudss ksdxfdmp

OR

..__sighandler _IO_vfprintf vsprintf     .. kcldle kclbsy ksudss ksdxfdmp



lms process:

..skgpwwait kslgess ksl_get_shared_latch kclpdc kclfpbl kclfbst kcl_fairness kclgeneratecr..

• hanganalyze wait cycle

    Oracle session identified by:
    {
                instance: 1 (<RACDB>.<RACDB1>)
                   os id: 31745
              process id: 14, oracle@<HOSTNAME> (LMS1)
              session id: 911
        session serial #: 1
    }
    is waiting for 'latch: gc element' with wait info:
    {
..
            time in wait: 1.126043 sec
      heur. time in wait: 42.069154 sec <<<<<<<<<<<
..

    }
    and is blocked by
 => Oracle session identified by:
    {
                instance: 1 (<RACDB>.<RACDB1>)
                   os id: 31711
              process id: 6, oracle@<HOSTNAME> (DIAG)
              session id: 391
        session serial #: 1
    }
    which is not in a wait

Changes

Cause

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