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ASM环境中有GC的等待事件的案例很少，今天就为大家分享一个老的案例，分享这个案例的本质不是想看最后的解决方案和定位的BUG，而是想分享一下ASM实例中的异常等待事件的分析方法其实跟普通数据库里时一样的，仍然可以通过hanganalyze和systemstate来分析，接下来我们就一起看看这个案例
1，环境介绍
这里大概的描述一下版本，有点老，11.2.0.4.2的版本，现在很少能看见这样的版本了。
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Oracle Database 11g Enterprise Edition Release 11.2.0.4.0 - 64bit Production
With the Partitioning, Real Application Clusters, Automatic Storage Management, OLAP,
Data Mining and Real Application Testing options
ORACLE_HOME = /u01/oracle/product/11.2.0
System name: AIX2，对ASM实例做HANGANALYZE与SYSTEMSTATE
这里对ASM实例做下面的操作不会生成很多的TRACE文件。
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oradebug setmypid
oradebug unlimit
oradebug hanganalyze 3
oradebug dump systemstate 2663，KILL MRP进程
ASM环境中还运行着数据库备库，此时通过recover managed standby database cancel想取消日志前滚，但是不能正常取消，唯有手动KILL MRP进程。KILL后再执行RECOVER MANAGED STANDBY DATABASE USING CURRENT LOGFILE DISCONNECT；日志前滚又恢复正常。
4，分析HANGANALYZE与SYSTEMSTATE日志
4.1 查看hanganalyze部分
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*** -03-31 20:09:59.453
===============================================================================
HANG ANALYSIS:
instances (db_name.oracle_sid): cdhtz_p780.cdhtz1
oradebug_node_dump_level: 3
os thread scheduling delay history: (sampling every 1.000000 secs)
0.000000 secs at [ 20:09:58 ]
NOTE: scheduling delay has not been sampled for 0.818740 secs 0.000000 secs from [ 20:09:54 - 20:09:59 ], 5 sec avg
0.000000 secs from [ 20:09:00 - 20:09:59 ], 1 min avg
0.000000 secs from [ 20:05:00 - 20:09:59 ], 5 min avg
vktm time drift history
===============================================================================
Chains most likely to have caused the hang:
[a] Chain 1 Signature: 'gc buffer busy release'<='buffer busy waits'
Chain 1 Signature Hash: 0xe473997a
[b] Chain 2 Signature: 'parallel recovery slave next change'<='buffer busy waits'
Chain 2 Signature Hash: 0x16abd035
[c] Chain 3 Signature: 'gc buffer busy release'<='buffer busy waits'
Chain 3 Signature Hash: 0xe473997a
===============================================================================
Non-intersecting chains:
-------------------------------------------------------------------------------
Chain 1:
-------------------------------------------------------------------------------
Oracle session identified by:
{
instance: 1 (cdhtz_p780.cdhtz1)
os id: 6226628
process id: 98, oracle@cdhtzrzdb1
session id: 255
session serial #: 451
}
is waiting for 'buffer busy waits' with wait info:
{
p1: 'file#'=0x7
p2: 'block#'=0x229d
p3: 'class#'=0x62
time in wait: 0.944766 sec (last interval)
time in wait: 76 min 54 sec (total)
timeout after: never
wait id: 135153
blocking: 0 sessions
wait history:
* time between current wait and wait #1: 0.000000 sec
1. event: 'latch: cache buffers chains'
time waited: 0.000017 sec
wait id: 152253 p1: 'address'=0x7000103deef8f58
p2: 'number'=0xb1
p3: 'tries'=0x0
* time between wait #1 and #2: 0.000000 sec
2. event: 'buffer busy waits'
time waited: 4.345775 sec (last interval)
time waited: 76 min 53 sec (total)
wait id: 135153 p1: 'file#'=0x7
p2: 'block#'=0x229d
p3: 'class#'=0x62
* time between wait #2 and #3: 0.000000 sec
3. event: 'latch: cache buffers chains'
time waited: 0.000012 sec
wait id: 152252 p1: 'address'=0x7000103deef8f58
p2: 'number'=0xb1
p3: 'tries'=0x0
}
and is blocked by
=> Oracle session identified by:
{
instance: 1 (cdhtz_p780.cdhtz1)
os id: 5767982
process id: 77, oracle@cdhtzrzdb1 (PR0E)
session id: 633
session serial #: 51
}
which is waiting for 'gc buffer busy release' with wait info:
{
p1: 'file#'=0x7
p2: 'block#'=0x229d
p3: 'class#'=0x62
time in wait: 0.923282 sec
heur. time in wait: 24 min 49 sec
timeout after: 0.076718 sec
wait id: 258197465
blocking: 2 sessions
wait history:
* time between current wait and wait #1: 0.000021 sec
1. event: 'gc buffer busy release'
time waited: 1.000014 sec
wait id: 258197464 p1: 'file#'=0x7
p2: 'block#'=0x229d
p3: 'class#'=0x62
* time between wait #1 and #2: 0.000012 sec
2. event: 'gc buffer busy release'
time waited: 1.000015 sec
wait id: 258197463 p1: 'file#'=0x7
p2: 'block#'=0x229d
p3: 'class#'=0x62
* time between wait #2 and #3: 0.000021 sec
3. event: 'gc buffer busy release'
time waited: 1.000039 sec
wait id: 258197462 p1: 'file#'=0x7
p2: 'block#'=0x229d
p3: 'class#'=0x62
}
Chain 1 Signature: 'gc buffer busy release'<='buffer busy waits'
Chain 1 Signature Hash: 0xe473997a
-------------------------------------------------------------------------------
-------------------------------------------------------------------------------
Chain 2:
-------------------------------------------------------------------------------
Oracle session identified by:
{
instance: 1 (cdhtz_p780.cdhtz1)
os id: 5963976
process id: 89, oracle@cdhtzrzdb1
session id: 2148
session serial #: 1613
}
is waiting for 'buffer busy waits' with wait info:
{
p1: 'file#'=0x3
p2: 'block#'=0x80
p3: 'class#'=0x11
time in wait: 67 min 44 sec
timeout after: never
wait id: 2843
blocking: 0 sessions
wait history:
* time between current wait and wait #1: 0.000077 sec
1. event: 'db file sequential read'
time waited: 0.006262 sec
wait id: 2842 p1: 'file#'=0x2
p2: 'block#'=0x2202
p3: 'blocks'=0x1
* time between wait #1 and #2: 0.000098 sec
2. event: 'db file sequential read'
time waited: 0.000507 sec
wait id: 2841 p1: 'file#'=0x2
p2: 'block#'=0x21ea
p3: 'blocks'=0x1
* time between wait #2 and #3: 0.000066 sec
3. event: 'db file sequential read'
time waited: 0.000380 sec
wait id: 2840 p1: 'file#'=0x2
p2: 'block#'=0x21e2
p3: 'blocks'=0x1
}
and is blocked by
=> Oracle session identified by:
{
instance: 1 (cdhtz_p780.cdhtz1)
os id: 8127092
process id: 84, oracle@cdhtzrzdb1 (PR0L)
session id: 1516
session serial #: 37
}
which is waiting for 'parallel recovery slave next change' with wait info:
{
time in wait: 0.008511 sec
heur. time in wait: 76 min 57 sec
timeout after: 0.001489 sec
wait id: 258195905
blocking: 1 session
wait history:
* time between current wait and wait #1: 0.000008 sec
1. event: 'parallel recovery slave next change'
time waited: 0.010020 sec
wait id: 258195904
* time between wait #1 and #2: 0.000004 sec
2. event: 'parallel recovery slave next change'
time waited: 0.010013 sec
wait id: 258195903
* time between wait #2 and #3: 0.000005 sec
3. event: 'parallel recovery slave next change'
time waited: 0.010016 sec
wait id: 258195902
}
Chain 2 Signature: 'parallel recovery slave next change'<='buffer busy waits'
Chain 2 Signature Hash: 0x16abd035
-------------------------------------------------------------------------------
===============================================================================
Intersecting chains:
-------------------------------------------------------------------------------
Chain 3:
-------------------------------------------------------------------------------
Oracle session identified by:
{
instance: 1 (cdhtz_p780.cdhtz1)
os id: 3146372
process id: 92, oracle@cdhtzrzdb1
session id: 2524
session serial #: 391
}
is waiting for 'buffer busy waits' with wait info:
{
p1: 'file#'=0x7
p2: 'block#'=0x229d
p3: 'class#'=0x62
time in wait: 7.613869 sec (last interval)
time in wait: 76 min 50 sec (total)
timeout after: never
wait id: 109934
blocking: 0 sessions
wait history:
* time between current wait and wait #1: 0.000000 sec
1. event: 'latch: cache buffers chains'
time waited: 0.000003 sec
wait id: 126021 p1: 'address'=0x7000103deef8f58
p2: 'number'=0xb1
p3: 'tries'=0x0
* time between wait #1 and #2: 0.000000 sec
2. event: 'buffer busy waits'
time waited: 3.531329 sec (last interval)
time waited: 76 min 42 sec (total)
wait id: 109934 p1: 'file#'=0x7
p2: 'block#'=0x229d
p3: 'class#'=0x62
* time between wait #2 and #3: 0.000000 sec
3. event: 'latch: cache buffers chains'
time waited: 0.000018 sec
wait id: 126020 p1: 'address'=0x7000103deef8f58
p2: 'number'=0xb1
p3: 'tries'=0x0
}
and is blocked by 'instance: 1, os id: 5767982, session id: 633',
which is a member of 'Chain 1'.
Chain 3 Signature: 'gc buffer busy release'<='buffer busy waits'
Chain 3 Signature Hash: 0xe473997a
-------------------------------------------------------------------------------这里可以连接到数据库进程的阻塞关系。
4.2 使用ass格式化systemstate
awk脚本可以让我们快速的了解systemstate中进程的等待事件和阻塞信息，可加速我们分析问题的效率。这里建议采用最新版本的ass1045的awk，它能展示更多的内容。
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[[email protected] ]$ awk -f ~/rs/sql/ass1045.awk cdhtz_ora_5046602.trc
Starting Systemstate 1
..............................................................................
.................
Ass.Awk Version 1.0.45
~~~~~~~~~~~~~~~~~~~~~~
Source file : cdhtz_ora_5046602.trc
System State 1 (2025-03-31 20:10:07.375)
~~~~~~~~~~~~~~ ~~~~~~~~~~~~~~~~~~~~~~~
1: [DEAD]
2: waiting for 'pmon timer'
3: waiting for 'rdbms ipc message'
4: waiting for 'VKTM Logical Idle Wait'
5: waiting for 'rdbms ipc message'
6: waiting for 'DIAG idle wait'
7: waiting for 'rdbms ipc message'
8: waiting for 'PING'
9: waiting for 'rdbms ipc message'
10: waiting for 'DIAG idle wait'
11: waiting for 'rdbms ipc message'
12: waiting for 'ges remote message'
13: waiting for 'gcs remote message'
14: waiting for 'gcs remote message'
15: waiting for 'rdbms ipc message'
16: waiting for 'GCR sleep'
17: waiting for 'rdbms ipc message'
18: waiting for 'rdbms ipc message'
19: waiting for 'rdbms ipc message'
20: waiting for 'rdbms ipc message'
21: waiting for 'rdbms ipc message'
22: waiting for 'rdbms ipc message'
23: waiting for 'smon timer'
24: waiting for 'rdbms ipc message'
25: waiting for 'rdbms ipc message'
26: waiting for 'ASM background timer'
27: waiting for 'rdbms ipc message'
28: waiting for 'rdbms ipc message'
29: waiting for 'RFS dispatch'
30: waiting for 'SQL*Net message from client'
31: waiting for 'wait for unread message on broadcast channel'
32: waiting for 'SQL*Net message from client'
33: waiting for 'rdbms ipc message'
34: waiting for 'rdbms ipc message'
35: waiting for 'rdbms ipc message'
36: waiting for 'class slave wait'
37: waiting for 'SQL*Net message from client'
38:
39: waiting for 'rdbms ipc message'
40: waiting for 'rdbms ipc message'
41: waiting for 'rdbms ipc message'
42: waiting for 'rdbms ipc message'
43: waiting for 'class slave wait'
44: waiting for 'rdbms ipc message'
45: waiting for 'rdbms ipc message'
46: waiting for 'SQL*Net message from client'
47: waiting for 'class slave wait'
48: waiting for 'class slave wait'
49:
50:
51: waiting for 'rdbms ipc message'
52: waiting for 'SQL*Net message from client'
53: waiting for 'RFS dispatch'
54: waiting for 'SQL*Net message from client'
55: waiting for 'SQL*Net message from client'
56: waiting for 'class slave wait'
57: waiting for 'MRP inactivation'
58: waiting for 'SQL*Net message from client'
59:
60: waiting for 'class slave wait'
61: waiting for 'parallel recovery slave next change'
62:
63: waiting for 'parallel recovery slave next change'
64: waiting for 'parallel recovery slave next change'
65: waiting for 'parallel recovery slave next change'
66: waiting for 'parallel recovery slave next change'
67: waiting for 'parallel recovery slave next change'
68: waiting for 'class slave wait'
69: waiting for 'class slave wait'
70: waiting for 'parallel recovery slave next change'
71: waiting for 'parallel recovery slave next change'
72: waiting for 'parallel recovery slave next change'
73: waiting for 'parallel recovery slave next change'
74: waiting for 'parallel recovery slave next change'
75: waiting for 'parallel recovery slave next change'
76: waiting for 'parallel recovery slave next change'
77: waiting for 'gc buffer busy release'
78: waiting for 'parallel recovery slave next change'
79: waiting for 'parallel recovery slave next change'
80: waiting for 'parallel recovery slave next change'
81: waiting for 'parallel recovery slave next change'
82: waiting for 'parallel recovery slave next change'
83: waiting for 'parallel recovery slave next change'
84: waiting for 'parallel recovery slave next change'
85: waiting for 'parallel recovery slave next change'
86: waiting for 'parallel recovery slave next change'
87: waiting for 'parallel recovery slave next change'
89: waiting for 'buffer busy waits' (0x3,0x80,0x11)[Buffer 0x00c00080]
Final Blocker: inst: 1, sid: 1516, ser: 37
91:
92: waiting for 'buffer busy waits' (0x7,0x229d,0x62)[Buffer 0x01c0229d]
Final Blocker: inst: 1, sid: 633, ser: 51
93: waiting for 'SQL*Net message from client'
96: waiting for 'direct path read'
97: waiting for 'SQL*Net message from client'
98: waiting for 'buffer busy waits' (0x7,0x229d,0x62)[Buffer 0x01c0229d]
Final Blocker: inst: 1, sid: 633, ser: 51
99: waiting for 'direct path read'
Blockers
~~~~~~~~
Above is a list of all the processes. If they are waiting for a resource
then it will be given in square brackets. Below is a summary of the
waited upon resources, together with the holder of that resource.
Notes:
~~~~~
o A process id of '???' implies that the holder was not found in the
systemstate. (The holder may have released the resource before we
dumped the state object tree of the blocking process).
o Lines with 'Enqueue conversion' below can be ignored *unless*
other sessions are waiting on that resource too. For more, see
http://gbr30026.uk.oracle.com:81/Public/TOOLS/Ass.html#enqcnv)
Resource Holder State
Buffer 0x00c00080 ??? Blocker
Buffer 0x01c0229d ??? Blocker
Warning: The following processes have multiple session state objects and
may not be properly represented above :
29: 53:
Object Names
~~~~~~~~~~~~
Buffer 0x00c00080
Buffer 0x01c0229d
Summary of Wait Events Seen (count>10)
~~~~~~~~~~~~~~~~~~~~~~~~~~~
No wait events seen more than 10 times4.3 查询gc buffer busy release会话信息
下面就是通过UE软件来定位详细的信息了，查看会话和等待事件信息。
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ROCESS 77: PR0E
----------------------------------------
SO: 0x7000103e48c42a0, type: 2, owner: 0x0, flag: INIT/-/-/0x00 if: 0x3 c: 0x3
proc=0x7000103e48c42a0, name=process, file=ksu.h LINE:12721 ID:, pg=0
(process) Oracle pid:77, ser:1, calls cur/top: 0x70001039b0808d0/0x70001039b0805f0
flags : (0x0) -
flags2: (0x30), flags3: (0x10)
intr error: 0, call error: 0, sess error: 0, txn error 0
intr queue: empty
ksudlp FALSE at location: 0
(post info) last post received: 704768 0 2
last post received-location: ksl2.h LINE:2374 ID:kslpsr
last process to post me: 0x7000103ea81a930 1 6
last post sent: 0 0 160
last post sent-location: kcb2.h LINE:4243 ID:kcbzww
last process posted by me: 0x7000103ea829260 5 0
(latch info) wait_event=704768 bits=0x0
Process Group: DEFAULT, pseudo proc: 0x7000103e29af078
O/S info: user: oracle, term: UNKNOWN, ospid: 5767982
OSD pid info: Unix process pid: 5767982, image: oracle@jklcrzdb1 (PR0E)
Short stack dump:
ksedsts()+240<-ksdxfstk()+44<-ksdxcb()+3432<-sspuser()+116<-__sighandler()<-thread_wait()+580<-sskgpwwait()+32<-skgpwwait()+180<-ksliwat()+10772<-kslwaitctx()+180<-kslwait()+112<-kclwlr()+644<-kcbzfc()+2708<-kcbr_media_apply()+1888<-krp_slave_apply()+344<-krp_slave_main()+1092<-ksvrdp()+1804<-opirip()+724<-opidrv()+608<-sou2o()+136<-opimai_real()+188<-ssthrdmain()+276<-main()+204<-__start()+112
----------------------------------------
SO: 0x7000103eaaf1038, type: 4, owner: 0x7000103e48c42a0, flag: INIT/-/-/0x00 if: 0x3 c: 0x3
proc=0x7000103e48c42a0, name=session, file=ksu.h LINE:12729 ID:, pg=0
(session) sid: 633 ser: 51 trans: 0x0, creator: 0x7000103e48c42a0
flags: (0x41) USR/- flags_idl: (0x1) BSY/-/-/-/-/-
flags2: (0x2080409) -/-/INC
DID: , short-term DID:
txn branch: 0x0
edition#: 0 oct: 0, prv: 0, sql: 0x0, psql: 0x0, user: 0/SYS
ksuxds FALSE at location: 0
service name: SYS$USERS
client details:
O/S info: user: oracle, term: UNKNOWN, ospid: 5767982
machine: jklcrzdb1 program: oracle@jklcrzdb1 (PR0E)
Current Wait Stack:
0: waiting for 'gc buffer busy release'
file#=0x7, block#=0x229d, class#=0x62
wait_id=258197477 seq_num=55118 snap_id=1
wait times: snap=0.007627 sec, exc=0.007627 sec, total=0.007627 sec
wait times: max=1.000000 sec, heur=24 min 59 sec
wait counts: calls=1 os=1
in_wait=1 iflags=0x5a8
There are 2 sessions blocked by this session.
Dumping one waiter:
inst: 1, sid: 255, ser: 451
wait event: 'buffer busy waits'
p1: 'file#'=0x7
p2: 'block#'=0x229d
p3: 'class#'=0x62
row_wait_obj#: 4294967295, block#: 0, row#: 0, file# 0
min_blocked_time: 2404 secs, waiter_cache_ver: 27635
Wait State:
fixed_waits=0 flags=0x22 boundary=0x0/-1下面GC正在等待的数据块的信息。
SO:
proc=0x7000103ea8281b8, name=call, file=ksu.h LINE:12725 ID:, pg=0
(call) sess: cur 7000103f8ec4eb0, rec 0, usr 7000103f8ec4eb0; flg:20 fl2:1; depth:0
svpt(xcb:0x0 sptn:0x4286 uba: 0x00000000.0000.00)
ksudlc FALSE at location: 0
----------------------------------------
SO: 0x7000103d4e2c040, type: 38, owner: 0x70001039b096df0, flag: INIT/-/-/0xc0 if: 0x1 c: 0x1
proc=0x7000103ea8281b8, name=buffer handle, file=kcb2.h LINE:2761 ID:, pg=0
(buffer) (CR) PR: 0x7000103ea8281b8 FLG: 0x0
lock rls: 0x700010029dc27d8, class bit: 0x0
cr[0]:
sh[0]:
kcbbfbp: [BH: 0x700010029dc27d8, LINK: 0x7000103d4e2c0c0] (WAITING)
type: normal pin
where: ktuwh27: kturbk, why: 0
BH (0x700010029dc27d8) file#: 7 rdba: 0x01c0229d (7/8861) class: 98 ba: 0x70001002896e000
set: 62 pool: 3 bsz: 8192 bsi: 0 sflg: 1 pwc: 0,0
dbwrid: 1 obj: -1 objn: -1 tsn: 2 afn: 7 hint: f
hash: [0x7000103e7d29d30,0x700010231e8cbf0] lru: [0x700010237e08048,0x700010117dcdec8]
lru-flags: on_auxiliary_list
ckptq: [NULL] fileq: [0x700010143e35aa8,0x700010237e07f68] objq: [0x700010143e35bb0,0x700010237e08070] objaq: [0x700010237e08080,0x700010117dcdf00]
use: [NULL] wait: [0x7000103d712cff0,0x7000103d4e2c0c0]
st: MEDIA_RCV md: NULL rsop: 0x700010394bdde40 tch: 1 le: 0x7000102f3ed7608 rlscn: 0x0bac.feaeaa51
flags: down_grade_lock only_sequential_access block_written_once
Waiting State Objects
----------------------------------------
SO: 0x7000103d712cf70, type: 38, owner: 0x70001039b0a69c0, flag: INIT/-/-/0xc0 if: 0x1 c: 0x1
proc=0x7000103ea829260, name=buffer handle, file=kcb2.h LINE:2761 ID:, pg=0
(buffer) (CR) PR: 0x7000103ea829260 FLG: 0x0
lock rls: 0x700010029dc27d8, class bit: 0x0
cr[0]:
sh[0]:
kcbbfbp: [BH: 0x700010029dc27d8, LINK: 0x7000103d712cff0] (WAITING)
type: normal pin
where: ktuwh27: kturbk, why: 0
----------------------------------------
SO: 0x7000103d4e2c040, type: 38, owner: 0x70001039b096df0, flag: INIT/-/-/0xc0 if: 0x1 c: 0x1
proc=0x7000103ea8281b8, name=buffer handle, file=kcb2.h LINE:2761 ID:, pg=0
(buffer) (CR) PR: 0x7000103ea8281b8 FLG: 0x0
lock rls: 0x700010029dc27d8, class bit: 0x0
cr[0]:
sh[0]:
kcbbfbp: [BH: 0x700010029dc27d8, LINK: 0x7000103d4e2c0c0] (WAITING)
type: normal pin
where: ktuwh27: kturbk, why: 0
GLOBAL CACHE ELEMENT DUMP (address: 0x7000102f3ed7608):
id1: 0x229d id2: 0x7 pkey: INVALID block: (7/8861)
lock: X rls: 0x7 acq: 0x0 latch: 10
flags: 0x20 fair: 255 recovery: 0 fpin: 'kclwh2'
bscn: 0xbac.feaeaa51 bctx: 0x0 write: 0 scan: 0x0
lcp: 0x0 lnk: [NULL] lch: [0x700010029dc2910,0x700010029dc2910]
seq: 1054 hist: 54 113 238 180 113 238 180 143:0 208 352 32 197 48 121 45 299
LIST OF BUFFERS LINKED TO THIS GLOBAL CACHE ELEMENT:
flg: 0x00280400 lflg: 0x4 state: MEDIA_RCV tsn: 2 tsh: 1
waiters: 2
addr: 0x700010029dc27d8 obj: INVALID cls: UNDO BLOCK bscn: 0xbac.feaeaa51
buffer tsn: 2 rdba: 0x01c0229d (7/8861)
scn: 0x0bac.feaeaa51 seq: 0x09 flg: 0x04 tail: 0xaa510209
frmt: 0x02 chkval: 0x3bf8 type: 0x02=KTU UNDO BLOCK这里大概定位到处问题的数据块、内存中的状态（state: MEDIA_RCV）了，这种特殊情况怀疑都是BUG导致。
5 处理办法
其实说到这儿，聪明的你肯定已经猜到------这多半又是个"祖传BUG"。于是我火速上MOS一搜，果然不出所料，发现了下面这个"熟悉的面孔"：
5.1 搜MOS发现如下BUG
Bug
Bug 17695685 Hang in Active Dataguard Database
This note gives a brief overview of bug 17695685.
The content was last updated on: 17-DEC-2014
Click here for details of each of the sections below.
Affects:
Product (Component)
Oracle Server (Rdbms)
Range of versions believed to be affected
Versions >= 11.2
Versions confirmed as being affected
• 11.2.0.4
• 11.2.0.3
Platforms affected
Generic (all / most platforms affected)
Fixed:
The fix for 17695685 is first included in
• (None Specified)
Interim patches may be available for earlier versions - click here to check.
Symptoms:
Related To:
• Hang (Process Hang)
• Waits for "gc buffer busy release"
• Active Dataguard (ADG)
• RAC (Real Application Clusters) / OPS
• MRP process
Description
This bug is only relevant when using Real Application Clusters (RAC)
Rediscovery:
- There is hang in Active Dataguard Database (ADG)
- MRP or its slave waits for a buffer with state: MEDIA_RCV
For example a hanganalyze trace might show something like:
Oracle session identified by:
{
instance: 1 (dtcpcta.dtcpcta1)
os id: 31520
process id: 82, oraclecolldtdbpr31 (PR0J)
session id: 982
session serial #: 1157
}
which is waiting for 'gc buffer busy release' with wait info:
{
p1: 'file#'=0x3
p2: 'block#'=0x1399a
p3: 'class#'=0x1c
time in wait: 0.567673 sec
heur. time in wait: 40 min 7 sec
timeout after: 0.432327 sec
wait id: 35008931
blocking: 2737 sessions
current sql: <none>
short stack:
ksedsts()+465<- ...
<-semtimedop()+10<-skgpwwait()+160<-ksliwat()+2022<-kslwaitctx()+163<-kslwait()+141
<-kclwlr()+535<-kcbzfc()+656<-kcbr_media_apply()+1782<-krp_slave_apply()+284<-krp_slave_main()
GLOBAL CACHE ELEMENT DUMP (address: 0xf7e7c360):
id1: 0x1399a id2: 0x3 pkey: INVALID block: (3/80282)
lock: X rls: 0x7 acq: 0x0 latch: 3
flags: 0x20 fair: 255 recovery: 0 fpin: 'kclwh2'
bscn: 0x2.3927d9d3 bctx: (nil) write: 0 scan: 0x0
lcp: (nil) lnk: [NULL] lch: [0x31f91f2b0,0x31f91f2b0]
seq: 89 hist: 54 113 238 180 113 238 180 113 238 180 113 238 180 113 238 180
113 238 180 113
LIST OF BUFFERS LINKED TO THIS GLOBAL CACHE ELEMENT:
flg: 0x00280400 lflg: 0x8 state: MEDIA_RCV tsn: 2 tsh: 4 waiters: 4
- There are waiters for "Media Recovery" buffer目前在AIX平台只有11.2.0.4.5下面有PATCH包，现在环境是11.2.0.4.2，需要先打PSU到11.2.0.4.5
5.2 关闭一个实例
可以先关闭一个实例就不会出现这个故障了。
5.3 配置参数
还有个"歪招"------把_fairness_threshold参数设成0，虽然能暂时压住BUG，但副作用是数据库性能会"自闭"，慎用慎用！
结尾示例
好啦，今天的"悬疑大戏"就到这里。遇到这种GC等待、MRP hang住的奇葩问题，别慌，按上面套路走一遍，基本都能搞定。实在不行，咱们还有MOS和补丁兜底。
码字不易，欢迎点赞、关注、转发，顺便点个小星星，祝大家数据库永远不卡，MRP永远不罢工！
------------------作者介绍-----------------------
姓名：黄廷忠
现就职：Oracle中国高级服务团队
曾就职：OceanBase、云和恩墨、东方龙马等
电话、微信、QQ：18081072613
