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Job Queue Slave Process Encounters High Buffer Busy Waits (Doc ID 2566973.1)

Last updated on JULY 01, 2021

Applies to:

Oracle Database - Enterprise Edition - Version and later
Information in this document applies to any platform.


You experience long wait times on wait event, 'buffer busy waits', by job queue slave processes (Jnnn).  The process is waiting to update table, SYS.SCHEDULER$_JOB, with OBJ# specified in the WHERE clause (with SQL ID 'g4gp07gt2z920').

Diagnostics hang-manager file output may look similar to the following.  Both job queue slave processes are attempting to update SYS.SCHEDULER$_JOB.

Short stack dump: ksedsts()+346<-ksdxfstk()+71<-ksdxcb()+912<-sspuser()+217<-__sighandler()<-__lll_lock_wait()+34<-00007F8B40B27AC0
HM: Current SQL: update sys.scheduler$_job set  last_start_date = :1, running_instance = :2, running_slave = :3, job_status = :4 where  obj# = :5   ◄◄◄ SQL ID 'g4gp07gt2z920'
                      SO: 0x2c83e6c40, type: 4, owner: 0x2c8050680, flag: INIT/-/-/-/0x00 if: 0x3 c: 0x3
                       proc=0x2c8050680, name=session, file=ksu.h LINE:15737, pg=1, conuid=0
                      (session) sid: 651 ser: 6624 trans: 0x2c7f803b0, creator: 0x2c8050680   
                                flags: (0x41) USR/- flags2: (0x40009) -/-/INC
                                flags_idl: (0x1) status: BSY/-/-/- kill: -/-/-/-
                                DID: 0001-009D-0000062A0001-009D-00000629, short-term DID:
                                txn branch: (nil)
                                edition#: 0                                user#/name: 0/SYS   
                                oct: 6, prv: 0, sql: 0x52e097e18, psql: 0x52faf4718
                                stats: 0x2abac85d0, PX stats: 0x110a9884
                      service name: SYS$USERS
                      client details:
                        O/S info: user: oracle, term: UNKNOWN, ospid: 64791_32737
                        machine: program: (J002)    ◄◄◄ Job queue slave
                      Current Wait Stack:
                        Not in wait; last wait ended 7 min 34 sec ago     ◄◄◄ Either running on a CPU, or waiting to be assigned to a CPU.
                      There are 1 sessions blocked by this session.
                      Dumping one waiter:
                        inst: 1, sid: 93, ser: 57345
                        wait event: 'buffer busy waits'
                          p1: 'file#'=0x1
                          p2: 'block#'=0x4699
                          p3: 'class#'=0x1
                        row_wait_obj#: 8877, block#: 18073, row#: 0, file# 1
                        min_blocked_time: 427 secs, waiter_cache_ver: 10225    ◄◄◄ Another job queue slave is waiting for busy buffer for at least 7 mins.
                      Wait State:
                        fixed_waits=0 flags=0x20 boundary=(nil)/-1
                      Session Wait History:
                          elapsed time of 7 min 34 sec since last wait
                       0: waited for 'enq: IV -  contention'
                          type|mode=0x49560005, id1=0x53594e43, id2=0xb7
                          wait_id=37 seq_num=38 snap_id=1
                          wait times: snap=0.000297 sec, exc=0.000297 sec, total=0.000297 sec
                          wait times: max=infinite
                          wait counts: calls=2 os=2
                          occurred after 0.000080 sec of elapsed time



 The instance-wide value of THREADED_EXECUTION is TRUE (whereas its default value is FALSE).


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