ORA-00494 enqueue [CF] held for too long故障分析處理

今天接應用人員電話反應，一套備份資料庫在加完表空間後出現異常，現象是資料庫能查詢，但是update很慢。


故障處理詳細：
1、檢視alert日誌如下：
Thread 1 advanced to log sequence 16541 (LGWR switch)
  Current log# 1 seq# 16541 mem# 0: +DATA/racdb/onlinelog/group_1.262.792077131
  Current log# 1 seq# 16541 mem# 1: +DATA/racdb/onlinelog/group_1.263.792077153
Fri Sep 12 09:52:51 2014
Archived Log entry 3480 added for thread 1 sequence 16540 ID 0x10fd7185 dest 1:
Fri Sep 12 09:59:08 2014
alter tablespace ALARM_DATA_TBS add datafile '+DATA' size 10g autoextend off
Fri Sep 12 10:01:11 2014
Completed: alter tablespace ALARM_DATA_TBS add datafile '+DATA' size 10g autoextend off
Fri Sep 12 10:06:17 2014
alter tablespace ALARM_DATA_TBS add datafile '+DATA' size 10g autoextend off
Fri Sep 12 10:13:44 2014
minact-scn: useg scan erroring out with error e:12751
Fri Sep 12 10:17:50 2014
Errors in file /oracle/app/oracle/diag/rdbms/racdb/racdb/trace/racdb_m001_18487.trc:
ORA-12751: cpu time or run time policy violation
Fri Sep 12 10:22:46 2014
Errors in file /oracle/app/oracle/diag/rdbms/racdb/racdb/trace/racdb_ora_17431.trc  (incident=362566):
ORA-00494: 持有入隊 [CF] 的時間過長 (超過 900 秒) (由 'inst 1, osid 18462')
Incident details in: /oracle/app/oracle/diag/rdbms/racdb/racdb/incident/incdir_362566/racdb_ora_17431_i362566.trc
Fri Sep 12 10:23:16 2014
Killing enqueue blocker (pid=18462) on resource CF-00000000-00000000 by (pid=17431)
by killing session 2140.29719
Attempt to get Control File Enqueue by USER pid=17431 (mode=X, type=0, timeout=900) is being blocked by inst=1, pid=18462
Please check inst 1's alert log for more information on the blocker including a possible ORA-00494 and related incident logs
Fri Sep 12 10:23:57 2014
minact-scn: useg scan erroring out with error e:12751
Fri Sep 12 10:23:57 2014
Sweep [inc][362566]: completed
Sweep [inc2][362566]: completed
Fri Sep 12 10:25:10 2014
Errors in file /oracle/app/oracle/diag/rdbms/racdb/racdb/trace/racdb_lgwr_9336.trc  (incident=360259):
ORA-00494: enqueue [CF] held for too long (more than 900 seconds) by 'inst 1, osid 18462'
Incident details in: /oracle/app/oracle/diag/rdbms/racdb/racdb/incident/incdir_360259/racdb_lgwr_9336_i360259.trc
Fri Sep 12 10:25:40 2014
Killing enqueue blocker (pid=18462) on resource CF-00000000-00000000 by (pid=9336)
by killing session 2140.29719
Attempt to get Control File Enqueue by LGWR pid=9336 (mode=X, type=0, timeout=900) is being blocked by inst=1, pid=18462
Please check inst 1's alert log for more information on the blocker including a possible ORA-00494 and related incident logs
Fri Sep 12 10:28:16 2014
Errors in file /oracle/app/oracle/diag/rdbms/racdb/racdb/trace/racdb_ora_17431.trc  (incident=362567):
ORA-00494: 持有入隊 [CF] 的時間過長 (超過 900 秒) (由 'inst 1, osid 18462')
Incident details in: /oracle/app/oracle/diag/rdbms/racdb/racdb/incident/incdir_362567/racdb_ora_17431_i362567.trc
Fri Sep 12 10:28:46 2014
Killing enqueue blocker (pid=18462) on resource CF-00000000-00000000 by (pid=17431)
by terminating the process
Attempt to get Control File Enqueue by USER pid=17431 (mode=X, type=0, timeout=300) is being blocked by inst=1, pid=18462
Please check inst 1's alert log for more information on the blocker including a possible ORA-00494 and related incident logs
Fri Sep 12 10:28:46 2014
Thread 1 advanced to log sequence 16542 (LGWR switch)
  Current log# 2 seq# 16542 mem# 0: +DATA/racdb/onlinelog/group_2.264.792077173
  Current log# 2 seq# 16542 mem# 1: +DATA/racdb/onlinelog/group_2.265.792077193




2、進入資料庫中手動切換日誌(alter system switch logfile)很慢幾近於不動。


3、分析日誌發現LGWR程式一直在等待CF enqueue，
Dump continued from file: /oracle/app/oracle/diag/rdbms/racdb/racdb/trace/racdb_lgwr_5854.trc 
ORA-00494: enqueue [CF] held for too long (more than 900 seconds) by 'inst 1, osid 7955' 


========= Dump for incident 380258 (ORA 494) ======== 
----- Beginning of Customized Incident Dump(s) ----- 
------------------------------------------------------------------------------- 
ENQUEUE [CF] HELD FOR TOO LONG 


enqueue holder: 'inst 1, osid 7955'
 
4、進一步分析發現很多次control file sequential read等待，即處於IO等待狀態，
為什麼出現control file sequential read，可能控制檔案不在了，或者控制檔案或其快照所在目錄掉了。
Current Wait Stack:
  Not in wait; last wait ended 17 min 35 sec ago 
There are 40 sessions blocked by this session.
Dumping one waiter:
  inst: 1, sid: 1653, ser: 1
  wait event: 'enq: CF - contention'
    p1: 'name|mode'=0x43460005
    p2: '0'=0x0
    p3: 'operation'=0x0
  row_wait_obj#: 4294967295, block#: 0, row#: 0, file# 0
  min_blocked_time: 898 secs, waiter_cache_ver: 407
Wait State:
  fixed_waits=0 flags=0x21 boundary=0x0/-1
Session Wait History:
    elapsed time of 17 min 35 sec since last wait
 0: waited for 'control file sequential read'
    file#=0x0, block#=0x12, blocks=0x1
    wait_id=10168 seq_num=10169 snap_id=1
    wait times: snap=0.000352 sec, exc=0.000352 sec, total=0.000352 sec
    wait times: max=infinite
    wait counts: calls=0 os=0
    occurred after 0.000018 sec of elapsed time
 1: waited for 'control file sequential read'
    file#=0x0, block#=0x10, blocks=0x1
    wait_id=10167 seq_num=10168 snap_id=1
    wait times: snap=0.000320 sec, exc=0.000320 sec, total=0.000320 sec
    wait times: max=infinite
    wait counts: calls=0 os=0
    occurred after 0.000018 sec of elapsed time




5、進入RMAN中檢視控制檔案備份路徑均為/oradata/racdbdb_rman_bak目錄，詳細如下：
 RMAN> show all;


使用目標資料庫控制檔案替代恢復目錄
db_unique_name 為 racdb 的資料庫的 RMAN 配置引數為:
CONFIGURE RETENTION POLICY TO REDUNDANCY 1;
CONFIGURE BACKUP OPTIMIZATION OFF; # default
CONFIGURE DEFAULT DEVICE TYPE TO DISK; # default
CONFIGURE CONTROLFILE AUTOBACKUP OFF;
CONFIGURE CONTROLFILE AUTOBACKUP FORMAT FOR DEVICE TYPE DISK TO '/oradata/racdbdb_rman_bak/conf_%T_%F';
CONFIGURE DEVICE TYPE DISK PARALLELISM 1 BACKUP TYPE TO BACKUPSET; # default
CONFIGURE DATAFILE BACKUP COPIES FOR DEVICE TYPE DISK TO 1; # default
CONFIGURE ARCHIVELOG BACKUP COPIES FOR DEVICE TYPE DISK TO 1; # default
CONFIGURE MAXSETSIZE TO UNLIMITED; # default
CONFIGURE ENCRYPTION FOR DATABASE OFF; # default
CONFIGURE ENCRYPTION ALGORITHM 'AES128'; # default
CONFIGURE COMPRESSION ALGORITHM 'BASIC' AS OF RELEASE 'DEFAULT' OPTIMIZE FOR LOAD TRUE ; # default
CONFIGURE ARCHIVELOG DELETION POLICY TO NONE; # default
CONFIGURE SNAPSHOT CONTROLFILE NAME TO '/oradata/racdbdb_rman_bak/snap_racdb.ctl'; 


6、檢視目錄發現/oradata目錄掉了
 bash-3.00$ df -h
Filesystem             size   used  avail capacity  Mounted on
/dev/dsk/c0t0d0s0       96G    47G    48G    50%    /
/devices                 0K     0K     0K     0%    /devices
ctfs                     0K     0K     0K     0%    /system/contract
proc                     0K     0K     0K     0%    /proc
mnttab                   0K     0K     0K     0%    /etc/mnttab
swap                    87G   1.9M    87G     1%    /etc/svc/volatile
objfs                    0K     0K     0K     0%    /system/object
sharefs                  0K     0K     0K     0%    /etc/dfs/sharetab
fd                       0K     0K     0K     0%    /dev/fd
swap                    87G   120K    87G     1%    /tmp
swap                    87G    80K    87G     1%    /var/run
/dev/dsk/c0t0d0s4       38G    27G    11G    72%    /export/home
/dev/dsk/c0t1d0s3       77G    41G    35G    54%    /oracle


7、通過修改控制檔案備份路徑，資料庫恢復正常。 
 RMAN> CONFIGURE SNAPSHOT CONTROLFILE NAME TO '/oracle/app/oracle/product/11.2.0/db_1/dbs/snap_racdb.ctl'; 
 RMAN> show all;


db_unique_name 為 racdb 的資料庫的 RMAN 配置引數為:
CONFIGURE RETENTION POLICY TO REDUNDANCY 1;
CONFIGURE BACKUP OPTIMIZATION OFF; # default
CONFIGURE DEFAULT DEVICE TYPE TO DISK; # default
CONFIGURE CONTROLFILE AUTOBACKUP ON;
CONFIGURE CONTROLFILE AUTOBACKUP FORMAT FOR DEVICE TYPE DISK TO '/oracle/app/oracle/product/11.2.0/db_1/dbs/conf_%T_%F';
CONFIGURE DEVICE TYPE DISK PARALLELISM 1 BACKUP TYPE TO BACKUPSET; # default
CONFIGURE DATAFILE BACKUP COPIES FOR DEVICE TYPE DISK TO 1; # default
CONFIGURE ARCHIVELOG BACKUP COPIES FOR DEVICE TYPE DISK TO 1; # default
CONFIGURE MAXSETSIZE TO UNLIMITED; # default
CONFIGURE ENCRYPTION FOR DATABASE OFF; # default
CONFIGURE ENCRYPTION ALGORITHM 'AES128'; # default
CONFIGURE COMPRESSION ALGORITHM 'BASIC' AS OF RELEASE 'DEFAULT' OPTIMIZE FOR LOAD TRUE ; # default
CONFIGURE ARCHIVELOG DELETION POLICY TO NONE; # default
CONFIGURE SNAPSHOT CONTROLFILE NAME TO '/oracle/app/oracle/product/11.2.0/db_1/dbs/snap_racdb.ctl'; 

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