[20181030]模拟分布式事务挂起导致TX锁争用.txt

来源：这里教程网时间：2026-03-03 12:11:14 作者：

[20181030]模拟分布式事务挂起导致TX锁争用.txt --//随着业务不断扩展,在业务中使用分布式事务的情况越来越多,除了导致scn抬高外,可能由于网络问题导致连接中断, --//甚至由于业务连接外部网络,比较常见ora-01591错误. $ oerr ora 1591 01591, 00000, "lock held by in-doubt distributed transaction %s" // *Cause: Trying to access resource that is locked by a dead two-phase commit // transaction that is in prepared state. // *Action: DBA should query the pending_trans$ and related tables, and attempt // to repair network connection(s) to coordinator and commit point. // If timely repair is not possible, DBA should contact DBA at commit // point if known or end user for correct outcome, or use heuristic // default if given to issue a heuristic commit or abort command to // finalize the local portion of the distributed transaction. --//网上有相关的文章提到如何解决这个问题. --//这里模拟分布式事务挂起导致TX锁争用,模拟出现ora-01591错误. --//测试参看链接:http://www.cnxdug.org/?p=1389 1.环境: --//客户端: SCOTT@book> @ ver1 PORT_STRING VERSION BANNER ------------------------------ -------------- -------------------------------------------------------------------------------- x86_64/Linux 2.4.xx 11.2.0.4.0 Oracle Database 11g Enterprise Edition Release 11.2.0.4.0 - 64bit Production SCOTT@book> create PUBLIC database link test033 connect to scott identified by btbtms using '192.168.100.33:1521/test:DEDICATED'; Database link created. SCOTT@book> create table deptx as select * from deptx; Table created. SCOTT@book> select sysdate from dual@test033; SYSDATE ------------------- 2018-10-31 08:55:34 --//OK,连接没有问题. SCOTT@book> commit; Commit complete. 2.测试: --//为了模拟分布式事务失败，无法自动恢复的情况，需要把分布式事务自动恢复关掉。 SCOTT@book> alter system disable distributed recovery; System altered. --//服务端: SCOTT@test> @ &r/ver1 PORT_STRING VERSION BANNER ------------------------------ -------------- ---------------------------------------------------------------- x86_64/Linux 2.4.xx 10.2.0.4.0 Oracle Database 10g Enterprise Edition Release 10.2.0.4.0 - 64bi SCOTT@test> create table depty as select * from dept; Table created. 2.在客户端执行: SCOTT@book> update deptx set loc = lower(loc) where deptno=10; 1 row updated. SCOTT@book> update depty@test033 set loc = lower(loc) where deptno=20; 1 row updated. SCOTT@book> @ &r/xid XIDUSN_XIDSLOT_XIDSQN ------------------------------ 10.2.24482 C70 XIDUSN XIDSLOT XIDSQN UBAFIL UBABLK UBASQN UBAREC STATUS USED_UBLK USED_UREC XID ADDR START_DATE FLAG ---------------------------------------------------------------------- ---------- ---------- ---------- ---------- ---------- ---------- ---------- ---------------- ---------- ---------- ---------------- ---------------- ------------------- ---------- ALTER SYSTEM DUMP UNDO BLOCK '_SYSSMU10_1197734989$' XID 10 2 24482; 10 2 24482 3 10115 4716 1 ACTIVE 1 1 0A000200A25F0000 0000000081BD0748 2018-10-31 08:56:30 4197891 ALTER SYSTEM DUMP UNDO HEADER '_SYSSMU10_1197734989$'; ALTER SYSTEM DUMP DATAFILE 3 BLOCK 10115; SCOTT@book> COMMIT COMMENT 'ORA-2PC-CRASH-TEST-4'; COMMIT COMMENT 'ORA-2PC-CRASH-TEST-4' * ERROR at line 1: ORA-02054: transaction 10.2.24482 in-doubt ORA-02059: ORA-2PC-CRASH-TEST-4 in commit comment SCOTT@book> @ &r/xid XIDUSN_XIDSLOT_XIDSQN ------------------------------ no rows selected --//已经没有事务. --//"COMMIT COMMENT 'ORA-2PC-CRASH-TEST-4'"这个命令，是Oracle用来强制分布式事务失败，4代表非提交点的分布式事务失败在 --//prepare后。其它数值代表的意思如下： 1 Crash commit point after collect 2 Crash non-commit-point site after collect 3 Crash before prepare (non-commit-point site) 4 Crash after prepare (non-commit-point site) ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 5 Crash commit point site before commit 6 Crash commit point site after commit 7 Crash non-commit-point site before commit 8 Crash non-commit-point site after commit 9 Crash commit point site before forget 10 Crash non-commit-point site before forget --//查询dba_2pc_pending视图: SCOTT@book> select local_tran_id, GLOBAL_TRAN_ID, state from dba_2pc_pending; LOCAL_TRAN_ID GLOBAL_TRAN_ID STATE ---------------------- ------------------------- ---------------- 10.2.24482 BOOK.e6127bf4.10.2.24482 prepared --//本地事务是10.2.24482(与前面能对上)，全局事务是BOOK.e6127bf4.10.2.24482，状态是prepared。 --//观察lock状态: SCOTT@book> @ &r/viewlock no rows selected --//没有lock. --//如果我们再去执行更新deptx表的同一行发现会话挂起，过了就会报ORA-01591，Oracle自动检测到了这行记录被分布式事务挂起，导 --//致更新失败。 SCOTT@book> update deptx set dname = lower(dname) where deptno=10; update deptx set dname = lower(dname) where deptno=10 * ERROR at line 1: ORA-01591: lock held by in-doubt distributed transaction 10.2.24482 --//挂起一小会后,出现提示. SCOTT@book> @ &r/viewlock no rows selected SCOTT@book> select local_tran_id, GLOBAL_TRAN_ID, state from dba_2pc_pending; LOCAL_TRAN_ID GLOBAL_TRAN_ID STATE ---------------------- ------------------------ ---------------- 10.2.24482 BOOK.e6127bf4.10.2.24482 prepared --//解决很简单: SYS@book> select local_tran_id, GLOBAL_TRAN_ID, state from dba_2pc_pending; LOCAL_TRAN_ID GLOBAL_TRAN_ID STATE ---------------------- ------------------------ ---------------- 10.2.24482 BOOK.e6127bf4.10.2.24482 forced commit --//state=forced commit. SYS@book> alter system enable distributed recovery; System altered. SYS@book> exec dbms_transaction.purge_lost_db_entry( '10.2.24482'); BEGIN dbms_transaction.purge_lost_db_entry( '10.2.24482'); END; * ERROR at line 1: ORA-06510: PL/SQL: unhandled user-defined exception ORA-06512: at "SYS.DBMS_TRANSACTION", line 105 ORA-06512: at line 1 --//我的测试前面alter system enable distributed recovery;,打开以后就可以提交了. SYS@book> select * from scott.deptx where deptno=10; DEPTNO DNAME LOC ---------- -------------- ------------- 10 ACCOUNTING new york SCOTT@book> select * from scott.depty@test033 where deptno=20; DEPTNO DNAME LOC ---------- -------------- ------------- 20 RESEARCH DALLAS --//本地修改了,而远程修改失败. --//链接:http://www.cnxdug.org/?p=1389,提到设置commit_point_strength参数,自己也重复测试看看. --//以下是转载:(操作我自己重新做了一次) 如何防止进行prepared状态如果分布式事务的操作，经常在某个重要的数据库实例上进行，那为了防止本地事务异常进入prepared状态无法自动回滚处理，就需要把这个重要节点的commit_point_strength参数改大为dblink数据库中最大值，这样这个节点在提交分布式事务时，本地事务是不进入 prepared状态的。如当前远程实例commit_point_strength为1，把本地节点的commit_point_strength改为100，修改这个参数需要重启数据库实例。 SYS@book> @ &r/hide commit_point_strength NAME DESCRIPTION DEFAULT_VALUE SESSION_VALUE SYSTEM_VALUE --------------------- ------------------------------------------------------------- ------------- ------------- ------------ commit_point_strength Bias this node has toward not preparing in a two-phase commit TRUE 1 1 SYS@book> alter system set commit_point_strength=100 scope=spfile; System altered. SYS@book> shutdown immediate ; Database closed. Database dismounted. ORACLE instance shut down. SYS@book> startup ORACLE instance started. Total System Global Area 634732544 bytes Fixed Size 2255792 bytes Variable Size 197133392 bytes Database Buffers 427819008 bytes Redo Buffers 7524352 bytes Database mounted. Database opened. SYS@book> show parameter commit_point_strength; NAME TYPE VALUE --------------------- ------- ----- commit_point_strength integer 100 --//再次模拟上面的过程： SCOTT@book> alter system disable distributed recovery; System altered. SCOTT@book> update deptx set loc = lower(loc)||'a' where deptno=10; 1 row updated. SCOTT@book> update depty@test033 set loc = lower(loc) where deptno=20; 1 row updated. SCOTT@book> @ &r/xid XIDUSN_XIDSLOT_XIDSQN ------------------------------ 10.8.24486 SCOTT@book> COMMIT COMMENT 'ORA-2PC-CRASH-TEST-4'; COMMIT COMMENT 'ORA-2PC-CRASH-TEST-4' * ERROR at line 1: ORA-02050: transaction 10.8.24486 rolled back, some remote DBs may be in-doubt ORA-02054: transaction 10.47.75654 in-doubt ORA-02059: ORA-2PC-CRASH-TEST-4 in commit comment ORA-02063: preceding 2 lines from TEST033 SCOTT@book> @ &r/xid XIDUSN_XIDSLOT_XIDSQN ------------------------------ no rows selected --//已经没有事务. SYS@book> select local_tran_id, GLOBAL_TRAN_ID, state from dba_2pc_pending; LOCAL_TRAN_ID GLOBAL_TRAN_ID STATE ---------------------- ------------------------ ---------------- 10.8.24486 BOOK.e6127bf4.10.8.24486 collecting --//state=collecting,但是不影响本地更新操作.更新deptx表发现可以更新，不再挂起和报错。 SCOTT@book> update deptx set loc = lower(loc)||'a' where deptno=10; 1 row updated. SCOTT@book> commit ; Commit complete. --//不过作者没测试完成, 在服务端查询: SCOTT@test> select * from depty; select * from depty * ERROR at line 1: ORA-01591: lock held by in-doubt distributed transaction 10.47.75654 SCOTT@test> select local_tran_id, GLOBAL_TRAN_ID, state from dba_2pc_pending; LOCAL_TRAN_ID GLOBAL_TRAN_ID STATE ---------------------- ------------------------ ---------------- 10.47.75654 BOOK.e6127bf4.10.8.24486 prepared --//state=prepared. SCOTT@test> update depty set loc = lower(loc) where deptno=20; update depty set loc = lower(loc) where deptno=20 * ERROR at line 1: ORA-01591: lock held by in-doubt distributed transaction 10.47.75654 --//解决方法参考网上解决ora-01591的文档. --//我这里执行如下: --//客户端: SYS@book> alter system enable distributed recovery; System altered. SYS@book> select local_tran_id, GLOBAL_TRAN_ID, state from dba_2pc_pending; no rows selected SCOTT@book> select * from deptx where deptno=10; DEPTNO DNAME LOC ---------- -------------- ------------- 10 accounting new yorka SCOTT@book> select * from depty@test033 where deptno=20; DEPTNO DNAME LOC ---------- -------------- ------------- 20 RESEARCH DALLAS --//服务端: SCOTT@test> select local_tran_id, GLOBAL_TRAN_ID, state from dba_2pc_pending; no rows selected --//commit_point_strength=100本地业务没有影响,但是远程存在问题,依旧出现ora-01591.当然我的测试使用alter system disable distributed recovery; --//并不算真正的模拟. 3.注意收尾工作: SYS@book> alter system reset commit_point_strength; System altered. --//重启数据库,检查参数commit_point_strength设置(略).