今天接应用人员电话反应，一套备份数据库在加完表空间后出现异常，现象是数据库能查询，但是update很慢。

故障处理详细：

1、查看alert日志如下：

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: 持有入队 [CF] 的时间过长 (超过 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: 持有入队 [CF] 的时间过长 (超过 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、进入数据库中手动切换日志(alter system switch logfile)很慢几近于不动。

3、分析日志发现LGWR进程一直在等待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、进一步分析发现很多次control file sequential read等待，即处于IO等待状态，

为什么出现control file sequential read，可能控制文件不在了，或者控制文件或其快照所在目录掉了。

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、进入RMAN中查看控制文件备份路径均为/oradata/racdbdb_rman_bak目录，详细如下：

RMAN> show all;

使用目标数据库控制文件替代恢复目录

db_unique_name 为 racdb 的数据库的 RMAN 配置参数为:

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、查看目录发现/oradata目录掉了

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、通过修改控制文件备份路径，数据库恢复正常。

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 为 racdb 的数据库的 RMAN 配置参数为:

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';