有客户反馈系统hang住,不能归档,需要我们紧急介入分析
节点1日志
出现redo不能归档，redo日志都已经被写满，人工执行了ALTER SYSTEM ARCHIVE LOG CURRENT,数据库就开始把redo全部归档,但是后面产生的redo又不能归档，当redo全部写满之后，数据库有出现大量log file switch (archiving needed)等待

Tue Sep 24 22:05:37 2013
Thread 1 advanced to log sequence 47282 (LGWR switch)
  Current log# 6 seq# 47282 mem# 0: +DATA/q9db/onlinelog/group_6.1244.818697409
Tue Sep 24 22:07:31 2013
ORACLE Instance q9db1 - Can not allocate log, archival required
Thread 1 cannot allocate new log, sequence 47283
All online logs needed archiving
  Current log# 6 seq# 47282 mem# 0: +DATA/q9db/onlinelog/group_6.1244.818697409
Tue Sep 24 22:28:17 2013
ALTER SYSTEM ARCHIVE LOG
Archived Log entry 259646 added for thread 1 sequence 47266 ID 0x354620c2 dest 1:
Tue Sep 24 22:28:18 2013
Thread 1 advanced to log sequence 47283 (LGWR switch)
  Current log# 7 seq# 47283 mem# 0: +DATA/q9db/onlinelog/group_7.1243.818697415
Archived Log entry 259647 added for thread 1 sequence 47267 ID 0x354620c2 dest 1:
Archived Log entry 259648 added for thread 1 sequence 47268 ID 0x354620c2 dest 1:
Archived Log entry 259649 added for thread 1 sequence 47269 ID 0x354620c2 dest 1:
Archived Log entry 259650 added for thread 1 sequence 47270 ID 0x354620c2 dest 1:
Archived Log entry 259651 added for thread 1 sequence 47271 ID 0x354620c2 dest 1:
Archived Log entry 259652 added for thread 1 sequence 47272 ID 0x354620c2 dest 1:
Tue Sep 24 22:28:28 2013
Archived Log entry 259653 added for thread 1 sequence 47273 ID 0x354620c2 dest 1:
Archived Log entry 259654 added for thread 1 sequence 47274 ID 0x354620c2 dest 1:
Archived Log entry 259655 added for thread 1 sequence 47275 ID 0x354620c2 dest 1:
Archived Log entry 259656 added for thread 1 sequence 47276 ID 0x354620c2 dest 1:
Archived Log entry 259657 added for thread 1 sequence 47277 ID 0x354620c2 dest 1:
Archived Log entry 259658 added for thread 1 sequence 47278 ID 0x354620c2 dest 1:
Archived Log entry 259659 added for thread 1 sequence 47279 ID 0x354620c2 dest 1:
Tue Sep 24 22:28:39 2013
Archived Log entry 259660 added for thread 1 sequence 47280 ID 0x354620c2 dest 1:
Archived Log entry 259661 added for thread 1 sequence 47281 ID 0x354620c2 dest 1:
Archived Log entry 259662 added for thread 1 sequence 47282 ID 0x354620c2 dest 1:
Tue Sep 24 22:29:39 2013
Thread 1 advanced to log sequence 47284 (LGWR switch)
  Current log# 8 seq# 47284 mem# 0: +DATA/q9db/onlinelog/group_8.1242.818697417
Tue Sep 24 22:31:18 2013
Thread 1 advanced to log sequence 47285 (LGWR switch)
  Current log# 16 seq# 47285 mem# 0: +DATA/q9db/onlinelog/group_16.1884.827003545
Thread 1 advanced to log sequence 47286 (LGWR switch)
  Current log# 17 seq# 47286 mem# 0: +DATA/q9db/onlinelog/group_17.1885.827003587

节点2日志
节点2中出现大量的IPC Send timeout

Tue Sep 24 15:22:19 2013
IPC Send timeout detected. Sender: ospid 4008 [oracle@q9db02.800best.com (PING)]
…………
Tue Sep 24 18:51:55 2013
IPC Send timeout detected. Sender: ospid 4008 [oracle@q9db02.800best.com (PING)]
Tue Sep 24 18:57:54 2013
IPC Send timeout detected. Sender: ospid 4008 [oracle@q9db02.800best.com (PING)]
Receiver: inst 1 binc 464003926 ospid 1566
Tue Sep 24 19:03:57 2013
IPC Send timeout detected. Sender: ospid 4008 [oracle@q9db02.800best.com (PING)]
Receiver: inst 1 binc 464003926 ospid 1566
Tue Sep 24 19:09:53 2013
IPC Send timeout detected. Sender: ospid 4008 [oracle@q9db02.800best.com (PING)]
…………
Tue Sep 24 20:22:00 2013
IPC Send timeout detected. Sender: ospid 4008 [oracle@q9db02.800best.com (PING)]

节点1因为不能归档hang住，节点2紧接着也就hang住。对节点1hang住之时对两个节点分别做systemstate dump,使用ass进行分析得到节点1和节点2的记录大体如下：
节点1

393:waiting for 'log file switch (archiving needed)'
394:waiting for 'log file switch (archiving needed)'
     Cmd: Insert
395:waiting for 'log file switch (archiving needed)'
     Cmd: Insert
397:waiting for 'log file switch (archiving needed)'
     Cmd: Insert
398:waiting for 'log file switch (archiving needed)'
     Cmd: Insert
451:waiting for 'SQL*Net message from client'
469:waiting for 'log file switch (archiving needed)'
     Cmd: Insert
470:waiting for 'log file switch (archiving needed)'
     Cmd: Insert
471:waiting for 'log file switch (archiving needed)'
     Cmd: Insert
618:waiting for 'log file switch (archiving needed)'
     Cmd: Insert
626:waiting for 'log file switch (archiving needed)'
     Cmd: Insert
NO BLOCKING PROCESSES FOUND

节点2

515:waiting for 'gc buffer busy acquire'
     Cmd: Insert
516:waiting for 'gc buffer busy acquire'
     Cmd: Insert
517:waiting for 'gc buffer busy acquire'
     Cmd: Insert
518:waiting for 'gc buffer busy acquire'
     Cmd: Insert
519:waiting for 'gc buffer busy acquire'
     Cmd: Insert
520:waiting for 'gc buffer busy acquire'
     Cmd: Select
521:waiting for 'gc current request'
     Cmd: Insert
522:waiting for 'enq: TX - row lock contention'[Enq TX-00BA0020-001E3E3C]
     Cmd: Select
523:waiting for 'gc buffer busy acquire'
     Cmd: Insert
524:waiting for 'SQL*Net message from client'
525:waiting for 'gc buffer busy acquire'
     Cmd: Insert
526:waiting for 'gc buffer busy acquire'
     Cmd: Insert
527:waiting for 'enq: TX - row lock contention'[Enq TX-00BA0020-001E3E3C]
     Cmd: Select
528:waiting for 'SQL*Net message from client'
529:waiting for 'gc buffer busy acquire'
     Cmd: Select
                    Resource Holder State
    Enq TX-0005001E-0022374F   223: waiting for 'gc current request'
    Enq TX-0047001B-002BCEB2   247: waiting for 'gc current request'
    Enq TX-015B001E-000041FF   330: waiting for 'gc current request'
    Enq TX-00010010-002EA7CD   179: waiting for 'gc current request'
    Enq TX-00BA0020-001E3E3C    ??? Blocker
Object Names
~~~~~~~~~~~~
Enq TX-0005001E-0022374F
Enq TX-0047001B-002BCEB2
Enq TX-015B001E-000041FF
Enq TX-00010010-002EA7CD
Enq TX-00BA0020-001E3E3C

通过这里,我们可以明白，节点2的很多事务hang住是因为请求gc current request，而该等待是因为节点1无法归档，有些block无法正常传输到节点2，导致节点2一直hang在这里，然后就出现IPC Send timeout;节点1上的事务阻塞甚至hang住是因为无法归档导致.到此需要定位的问题是为什么节点1不能归档
继续分析节点1 alert日志

Tue Sep 24 15:18:20 2013
opidrv aborting process O000 ospid (7332) as a result of ORA-28
Immediate Kill Session#: 1904, Serial#: 1065
Immediate Kill Session: sess: 0x24a2522a38  OS pid: 7338
Immediate Kill Session#: 3597, Serial#: 11107
Immediate Kill Session: sess: 0x24c27cf498  OS pid: 7320
Tue Sep 24 15:18:23 2013
opidrv aborting process W000 ospid (7980) as a result of ORA-28
Tue Sep 24 15:18:23 2013
opidrv aborting process W001 ospid (8560) as a result of ORA-28
Tue Sep 24 15:18:35 2013
LGWR: Detected ARCH process failure
LGWR: Detected ARCH process failure
LGWR: Detected ARCH process failure
LGWR: Detected ARCH process failure
LGWR: STARTING ARCH PROCESSES
Tue Sep 24 15:18:35 2013
ARC0 started with pid=66, OS id=10793
Tue Sep 24 15:18:35 2013
Errors in file /u01/app/oracle/diag/rdbms/q9db/q9db1/trace/q9db1_nsa2_12635.trc:
ORA-00028: your session has been killed
LNS: Failed to archive log 8 thread 1 sequence 47156 (28)
ARC0: Archival started
LGWR: STARTING ARCH PROCESSES COMPLETE
Thread 1 advanced to log sequence 47157 (LGWR switch)
ARC0: STARTING ARCH PROCESSES
  Current log# 9 seq# 47157 mem# 0: +DATA/q9db/onlinelog/group_9.1241.818697421
Tue Sep 24 15:18:36 2013
ARC1 started with pid=81, OS id=10805
Tue Sep 24 15:18:36 2013
ARC2 started with pid=84, OS id=10807
Tue Sep 24 15:18:36 2013
ARC3 started with pid=87, OS id=10809
ARC1: Archival started
ARC2: Archival started
ARC2: Becoming the 'no FAL' ARCH
ARC2: Becoming the 'no SRL' ARCH
ARC1: Becoming the heartbeat ARCH
Error 1031 received logging on to the standby
PING[ARC1]: Heartbeat failed to connect to standby 'q9adgdg'. Error is 1031.
ARC3: Archival started
ARC0: STARTING ARCH PROCESSES COMPLETE
Archived Log entry 259135 added for thread 1 sequence 47156 ID 0x354620c2 dest 1:
Error 1031 received logging on to the standby
FAL[server, ARC3]: Error 1031 creating remote archivelog file 'q9adgdg'
FAL[server, ARC3]: FAL archive failed, see trace file.
ARCH: FAL archive failed. Archiver continuing
ORACLE Instance q9db1 - Archival Error. Archiver continuing.
Tue Sep 24 15:18:46 2013
opidrv aborting process O001 ospid (9605) as a result of ORA-28
Tue Sep 24 15:18:46 2013
opidrv aborting process O000 ospid (10813) as a result of ORA-28
Tue Sep 24 15:18:46 2013
Immediate Kill Session#: 2909, Serial#: 369
Immediate Kill Session: sess: 0x24226c7200  OS pid: 9091
Immediate Kill Session#: 3380, Serial#: 30271
Immediate Kill Session: sess: 0x2422782c58  OS pid: 10265
Immediate Kill Session#: 3597, Serial#: 11109
Immediate Kill Session: sess: 0x24c27cf498  OS pid: 10267
Tue Sep 24 15:20:14 2013
Restarting dead background process DIAG
Tue Sep 24 15:20:14 2013
DIAG started with pid=64, OS id=20568
Restarting dead background process PING
Tue Sep 24 15:20:14 2013
PING started with pid=68, OS id=20570
Restarting dead background process LMHB
Tue Sep 24 15:20:14 2013
LMHB started with pid=70, OS id=20572
Restarting dead background process SMCO
…………
Tue Sep 24 15:23:13 2013
ARC0: Detected ARCH process failure
Tue Sep 24 15:23:13 2013
Thread 1 advanced to log sequence 47158 (LGWR switch)
  Current log# 10 seq# 47158 mem# 0: +DATA/q9db/onlinelog/group_10.1240.818697423
ARC0: STARTING ARCH PROCESSES
ARC0: STARTING ARCH PROCESSES COMPLETE
ARC0: Becoming the heartbeat ARCH
ARCH: Archival stopped, error occurred. Will continue retrying
ORACLE Instance q9db1 - Archival Error
ORA-00028: your session has been killed

查看ARCn进程

[oracle@q9db01 ~]$ ps -ef|grep ora_ar
oracle   20718 12870  0 22:07 pts/14   00:00:00 grep ora_ar
[oracle@q9db01 ~]$ ps -ef|grep ora_ar
oracle   25998 12870  0 22:07 pts/14   00:00:00 grep ora_ar

这里基本上明白了，因为客户的系统从15:15开始由于中间件程序异常，导致大量会话连接数据库,然后dba为了防止其他业务不受影响,然后开始大量通过alter system kill session,误杀了不少系统进程，包括ARCn(0,1,2,3)进程,在后面ARCn进程因为某种原因无法正常启动,导致redo无法归档，所有的redo组写满系统即hang住，该系统由于大量kill session已经导致了实例本身异常(正常情况ARCn进程kill之后会自动重启),处理方案:先增加redo组配合定时人工归档，等待业务低峰重启节点1，解决问题。温馨提醒：kill进程请小心