数据库hang等待链分析利器

以你之姓@ 2022-10-17 05:30 175阅读 0赞

Oracle有时会出现hang住的现象，原因可能很多，例如资源争用，如果需要知道为什么出现hang，可以分析等待链，而使用hanganalyze是其中一种方式，今天尝试一下。

首先，我们模拟场景，会话1，更新test表的第一行记录，但是不提交，

SQL> select sid from v$mystat where rownum=1;  
      SID
    ----------
      42
    
    
    SQL> update test set object_id=1 where rownum=1;
    1 row updated.

会话2，更新相同行，此时出现了hang，

SQL> update test set object_id=1 where rownum=1;

会话3，更新相同行，还是出现了hang，

SQL> update test set object_id=1 where rownum=1;

可能当Oracle在hang状态下正常的sqlplus已经不能连上，从10g开始，提供了另外一种登陆方式，就是带着prelim，

[oracle@bisal ~]$ sqlplus -prelim / as sysdba
    
    
    SQL*Plus: Release 19.0.0.0.0 - Production on Fri Apr 23 09:03:52 2021
    Version 19.3.0.0.0
    
    
    Copyright (c) 1982, 2019, Oracle.  All rights reserved.

P.S. prelim的意思是preliminary connection

可以指定3级的hanganalyze，

SQL> oradebug hanganalyze 3
    Statement processed.

不同的LEVEL打印的内容是不同的，当然级别越高，打印越多，消耗就会高，

> 1-2：Only HANGANALYZE output, no process dump at all(只有hanganalyeze输出,不dump任何进程)
> 
> 3：Level 2 + Dump only processes thought to be in a hang (IN\_HANG state)(DUMP IN\_HANGE状态的进程)
> 
> 4：Level 3 + Dump leaf nodes (blockers) in wait chains (LEAF,LEAF\_NW,IGN\_DMP state)
> 
> 5：Level 4 + Dump all processes involved in wait chains (NLEAF state)
> 
> 10：Dump all processes (IGN state)

如果是CDB环境，要确认是CDB级别的hang还是PDB级别的hang。如果是PDB级别的hang，只需要收集PDB的信息。如果无法确认，建议收集一下CDB的信息。

从11.2.0.2起，使用"sqlplus -prelim"登陆后，hanganalyze不再有内容输出，因为需要一个进程状态对象和一个会话状态对象。所以执行hanganalyze分析后，只是显示执行成功，trace中只会记录，

HANG ANALYSIS:
    
    
    ERROR: Can not perform hang analysis dump without a process
           state object and a session state object.
      ( process=(nil), sess=(nil) )

正常连接执行hanganalyze，会显示打印的trace文件路径和名称，

[oracle@bisal ~]$ sys
    SQL*Plus: Release 19.0.0.0.0 - Production on Fri Apr 23 09:05:19 2021
    Version 19.3.0.0.0
    Copyright (c) 1982, 2019, Oracle.  All rights reserved.
    Connected to:
    Oracle Database 19c Enterprise Edition Release 19.0.0.0.0 - Production
    Version 19.3.0.0.0
    
    
    SQL> oradebug hanganalyze 3
    Hang Analysis in /opt/oracle/diag/rdbms/bisalcdb/BISALCDB/trace/BISALCDB_ora_47241.trc

从文件中，可以看到当前系统中存在两条等待链，等待事件都是enq: TX - row lock contention，Chain 1的会话是被sid=42的初始会话阻塞，Chain 2的会话同样被sid=42阻塞(which is a member of 'Chain 1')，

===============================================================================
    
    
    Chains most likely to have caused the hang:
     [a] Chain 1 Signature: 'SQL*Net message from client'<='enq: TX - row lock contention'
         Chain 1 Signature Hash: 0x38c48850
     [b] Chain 2 Signature: 'SQL*Net message from client'<='enq: TX - row lock contention'
         Chain 2 Signature Hash: 0x38c48850
    
    
    ===============================================================================
    Non-intersecting chains:
    
    
    -------------------------------------------------------------------------------
    Chain 1:
    -------------------------------------------------------------------------------
        Oracle session identified by:
        {
                    instance: 1 (bisalcdb.bisalcdb)
                       os id: 41963
                  process id: 51, oracle@bisal
                  session id: 79
            session serial #: 18025
                 module name: 5 (SQL*Plusbisal (TNS V1-V3))
                      pdb id: 5 (BISALPDB2)
        }
        is waiting for 'enq: TX - row lock contention' with wait info:
        {
                          p1: 'name|mode'=0x54580006
                          p2: 'usn<<16 | slot'=0x5000a
                          p3: 'sequence'=0x465
                time in wait: 1 min 42 sec
               timeout after: never
                     wait id: 25
                    blocking: 0 sessions
              current sql_id: 2786213102
                 current sql: update test set object_id=1 where rownum = 1
                 short stack: ksedsts()+426<-ksdxfstk()+58<-ksdxcb()+872<-sspuser()+200<-__sighandler()<-semtimedop()+10<-skgpwwait()+187<-ksliwat()+2218<-kslwaitctx()+188<-ksqcmi()+21656<-ksqgtlctx()+6620<-ksqgelctx()+838<-ktuGetTxForXid()+230<-ktcwit1()+367<-kdddgb()+5478<-kdusru()+458<-updrowFastPath()+1209<-qerupUpdRow()+1548<-qerupFetch()+471<-updaul()+1416<-updThreePhaseExe()+340<-updexe()+405<-opiexe()+11573<-kpoal8()+2387<-opiodr()+1202<-ttcpip()+1222<-opitsk()+1895<-opiino()+936<-opiodr()+1202<-opidrv()+1094<-sou2o()+165<-opimai_real(
                wait history:
                  * time between current wait and wait #1: 0.044253 sec
                  1.       event: 'SQL*Net message from client'
                     time waited: 13.489353 sec
                         wait id: 24               p1: 'driver id'=0x54435000
                                                   p2: '#bytes'=0x1
                  * time between wait #1 and #2: 0.000000 sec
                  2.       event: 'SQL*Net message to client'
                     time waited: 0.000001 sec
                         wait id: 23               p1: 'driver id'=0x54435000
                                                   p2: '#bytes'=0x1
                  * time between wait #2 and #3: 0.000011 sec
                  3.       event: 'SQL*Net message from client'
                     time waited: 0.000027 sec
                         wait id: 22               p1: 'driver id'=0x54435000
                                                   p2: '#bytes'=0x1
    }
        and is blocked by
     => Oracle session identified by:
        {
                    instance: 1 (bisalcdb.bisalcdb)
                       os id: 18256
                  process id: 46, oracle@bisal
                  session id: 42
            session serial #: 18536
                 module name: 5 (SQL*Plusbisal (TNS V1-V3))
                      pdb id: 5 (BISALPDB2)
        }
        which is waiting for 'SQL*Net message from client' with wait info:
        {
                          p1: 'driver id'=0x54435000
                          p2: '#bytes'=0x1
                time in wait: 2 min 6 sec
               timeout after: never
                     wait id: 82
                    blocking: 1 session
              current sql_id: 0
                 current sql: <none>
                 short stack: ksedsts()+426<-ksdxfstk()+58<-ksdxcb()+872<-sspuser()+200<-__sighandler()<-read()+14<-snttread()+16<-nttfprd()+354<-nsbasic_brc()+399<-nioqrc()+438<-opikndf2()+999<-opitsk()+905<-opiino()+936<-opiodr()+1202<-opidrv()+1094<-sou2o()+165<-opimai_real()+422<-ssthrdmain()+417<-main()+256<-__libc_start_main()+245
                wait history:
                  * time between current wait and wait #1: 0.000007 sec
                  1.       event: 'SQL*Net message to client'
                     time waited: 0.000001 sec
                         wait id: 81               p1: 'driver id'=0x54435000
                                                   p2: '#bytes'=0x1
                  * time between wait #1 and #2: 0.001595 sec
                  2.       event: 'db file scattered read'
                     time waited: 0.005296 sec
                         wait id: 80               p1: 'file#'=0x13
                                                   p2: 'block#'=0x763
                                                   p3: 'blocks'=0x5
                  * time between wait #2 and #3: 0.000287 sec
                  3.       event: 'db file sequential read'
                     time waited: 0.019587 sec
                         wait id: 79               p1: 'file#'=0x13
                                                   p2: 'block#'=0x762
                                                   p3: 'blocks'=0x1
        }
    
    
    Chain 1 Signature: 'SQL*Net message from client'<='enq: TX - row lock contention'
    Chain 1 Signature Hash: 0x38c48850
    -------------------------------------------------------------------------------
    
    
    ===============================================================================
    
    
    Intersecting chains:
    
    
    -------------------------------------------------------------------------------
    Chain 2:
    -------------------------------------------------------------------------------
        Oracle session identified by:
        {
                    instance: 1 (bisalcdb.bisalcdb)
                       os id: 41963
                  process id: 51, oracle@bisal
                  session id: 79
            session serial #: 18025
                 module name: 5 (SQL*Plusbisal (TNS V1-V3))
                      pdb id: 5 (BISALPDB2)
        }
        is waiting for 'enq: TX - row lock contention' with wait info:
        {
                          p1: 'name|mode'=0x54580006
                          p2: 'usn<<16 | slot'=0x5000a
                          p3: 'sequence'=0x465
                time in wait: 4 min 40 sec
               timeout after: never
                     wait id: 25
                    blocking: 0 sessions
              current sql_id: 2786213102
                 current sql: update test set object_id=1 where rownum = 1
                 short stack: ksedsts()+426<-ksdxfstk()+58<-ksdxcb()+872<-sspuser()+200<-__sighandler()<-semtimedop()+10<-skgpwwait()+187<-ksliwat()+2218<-kslwaitctx()+188<-ksqcmi()+21656<-ksqgtlctx()+6620<-ksqgelctx()+838<-ktuGetTxForXid()+230<-ktcwit1()+367<-kdddgb()+5478<-kdusru()+458<-updrowFastPath()+1209<-qerupUpdRow()+1548<-qerupFetch()+471<-updaul()+1416<-updThreePhaseExe()+340<-updexe()+405<-opiexe()+11573<-kpoal8()+2387<-opiodr()+1202<-ttcpip()+1222<-opitsk()+1895<-opiino()+936<-opiodr()+1202<-opidrv()+1094<-sou2o()+165<-opimai_real(
                wait history:
                  * time between current wait and wait #1: 0.044253 sec
                  1.       event: 'SQL*Net message from client'
                     time waited: 13.489353 sec
                         wait id: 24               p1: 'driver id'=0x54435000
                                                   p2: '#bytes'=0x1
                  * time between wait #1 and #2: 0.000000 sec
                  2.       event: 'SQL*Net message to client'
                     time waited: 0.000001 sec
                         wait id: 23               p1: 'driver id'=0x54435000
                                                   p2: '#bytes'=0x1
                  * time between wait #2 and #3: 0.000011 sec
                  3.       event: 'SQL*Net message from client'
                     time waited: 0.000027 sec
                         wait id: 22               p1: 'driver id'=0x54435000
                                                   p2: '#bytes'=0x1
        }
        and is blocked by 'instance: 1, os id: 18256, session id: 42',
        which is a member of 'Chain 1'.
    
    
    Chain 2 Signature: 'SQL*Net message from client'<='enq: TX - row lock contention'
    Chain 2 Signature Hash: 0x38c48850
    -------------------------------------------------------------------------------
    
    
    ===============================================================================

因此，从这个trace文件中，就可以很清晰地看到等待链的逻辑关系，进而有针对性的管理会话。

**近期更新的文章：**

《[会议交流的一些杂谈][Link 1]》

《[imp执行错误IMP-00010][imp_IMP-00010]》

《[找到系统视图定义的几种操作][Link 2]》

《[NULL判断对SQL的影响][NULL_SQL]》

《[曾经运维生涯中的几个“最”][Link 3]》

**文章分类和索引：**

《[公众号700篇文章分类和索引][700]》

[Link 1]: http://mp.weixin.qq.com/s?__biz=MzI2NzM1OTM4OA%3D%3D&chksm=ea82a7a2ddf52eb46af1f228aff9ee58cdb06375aa6e9cc304bcb8ecc9cc1f7f94f1f1b9a44f&idx=1&mid=2247492177&scene=21&sn=18fc61ccb334bac37dc9b091f4b32f7f#wechat_redirect
[imp_IMP-00010]: http://mp.weixin.qq.com/s?__biz=MzI2NzM1OTM4OA%3D%3D&chksm=ea82a7baddf52eac0fed11d0b20acde13d874f8c14bb36aa7dc642318fc08d0214c1af7a32f7&idx=1&mid=2247492169&scene=21&sn=6b6a65d66fc3673ea426268b6ffeaac8#wechat_redirect
[Link 2]: http://mp.weixin.qq.com/s?__biz=MzI2NzM1OTM4OA%3D%3D&chksm=ea82a7cfddf52ed91cd19b9f99d1297c0b39ba48b7dcd815f1dfeeee1ffa1a2fd318b74510c3&idx=1&mid=2247492156&scene=21&sn=96ad5acb34f7ce8ee6c17c02ea1ffaad#wechat_redirect
[NULL_SQL]: http://mp.weixin.qq.com/s?__biz=MzI2NzM1OTM4OA%3D%3D&chksm=ea82a7c5ddf52ed323d754ab80899ff4fc065453dc23e16b96e367d2f06d6dff3205950028ef&idx=1&mid=2247492150&scene=21&sn=128e815af4e8a0d7986889fc571b7233#wechat_redirect
[Link 3]: http://mp.weixin.qq.com/s?__biz=MzI2NzM1OTM4OA%3D%3D&chksm=ea82a7f2ddf52ee49775b374898978d2f13624f1e51dcbfecdfdd32925332132e4eaa88cc7bd&idx=1&mid=2247492097&scene=21&sn=f2c338461919594062136eb10a70e9c4#wechat_redirect
[700]: http://mp.weixin.qq.com/s?__biz=MzI2NzM1OTM4OA%3D%3D&chksm=ea82a5dfddf52cc949a5b8b316ee905927ff399713b34aec7d806c656e8ada09bfb562c039ca&idx=1&mid=2247491628&scene=21&sn=83bd320bd28da84501fada2e8d515e77#wechat_redirect