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Oracle 的 enq: TT - contention 等待事件

在遇到 TT 锁等待时,你可能会被Oracle的文档所困扰。即便是在Oracle Database 12c的文档中,关于TT锁的描述也是:Temporary table enqueue。

这其实已经不准确了,从数据库中可以得到更详细和准确的描述,V$LOCK_TYPE中有着准确记录:

SQL> set serveroutput on
SQL> exec print_table('select * from v$lock_type where type=''TT''');
TYPE                          : TT
NAME                          : Tablespace
ID1_TAG                       : tablespace ID
ID2_TAG                       : operation
IS_USER                       : NO
DESCRIPTION                   : Serializes DDL operations on tablespaces
-----------------

PL/SQL procedure successfully completed.

在Oracle 8i之后,这个事件代表的是表空间事务,用于防范死锁,TT - Tablespace Transaction。其两个核心参数: ID1 代表表空间号,ID2 代表操作类型。

操作类型代码的主要解释为:

0- is used to avoid the deadlock occurred between drop tablespace and create rollback segment
1- using in a given tablespace create data files In a serialized
2- is used to avoid TSPITR tablespace point in in time recovery during other types of operation
4- is used to create tablespace to block the tablespace ID
8- is used to avoid deadlock in ALTER during TABLESPACE
16- is the 16 hexadecimal 0 × 10, used to synchronize the allocation and recovery disc area, allocation and deallocation of extents.
32+ With the increase in 32+ data file add datafile and create a table space, where ID2 is 32 (decimal) + relative file number relative file number

参考链接:http://www.programering.com/a/MTMxMjNwATc.html


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By eygle on 2015-05-07 12:20 | Comments (0) | FAQ | 3168 |


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