oracle deadlock 之（二）

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        官网对oracle deadlock的说明　　http://docs.oracle.com/cd/E11882_01/server.112/e40540/consist.htm#CNCPT1339
　　
　　关于oracle lock介绍，参考下面的链接
　　http://blog.itpub.net/28697282/viewspace-1484385/
　　
　　什么是deadlock
　　官方给出的说法是
　　     A deadlock is a situation in which two or more users are waiting for data locked by each other. Deadlocks prevent some transactions from continuing to work.
　　      死锁是两个或者多个用户等待被对方锁定的数据的情况。也就是说两个或者多个用户互相等待对方所占有的资源的情况。
　　
　　deadlock的形成
　　
　　
　　
　　deadlock的检测
　　
　　        Oracle Database automatically detects deadlocks and resolves them by rolling back one statement involved in the deadlock,>statement-level rollback. The statement rolled back belongs to the transaction that detects the deadlock. Usually, the signalled transaction should be rolled back explicitly, but it can retry the rolled-back statement after waiting.
　　oracle 自动检测并解决deadlock，通过回滚deadlock中相关的
　　
　　与deadlock相关的进程（11g)
　　与oracle deadlock相关的进程官网说明
　　http://docs.oracle.com/cd/E11882_01/server.112/e40402/bgprocesses.htm#REFRN104
　　
　　下面是11g特有的检测死锁的两个进程 dia0，lmd0 
　　
Name　　
Expanded Name　　
Short Description　　
Long Description　　
External Properties　　
DIA0　　
Diagnostic Process　　
Detects and resolves hangs and deadlocks　　
　　
ASM and Database instances　　
LMD0　　
Global Enqueue Service Daemon 0 Process　　
Manages incoming remote resource requests from other instances　　
LMD0 processes enqueue resources managed under Global Enqueue Service. In particular, LMD0 processes incoming enqueue request messages and controls access to global enqueues. It also performs distributed deadlock detections.　　
Database and ASM instances, Oracle RAC　　
　　
　　
　　
　　
　　
　　
　　
　　deadlock模拟