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
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