oracle11g添加删除字段 ddl_time_out

SQL> set timing on

SQL> alter table test add (name varchar(2));

Table altered.

Elapsed: 00:00:00.08

SQL> alter table test drop column name;

Table altered.

Elapsed: 00:00:03.42

SQL> insert into test select * from test;

1385280 rows created.

Elapsed: 00:00:55.21

SQL> commit;

Commit complete.

Elapsed: 00:00:00.04

SQL> alter table test add (name varchar(2));

Table altered.

Elapsed: 00:00:00.07

SQL> alter table test drop column name;

Table altered.

Elapsed: 00:00:16.29

添加not null的带默认值的也很快了，之前有写。有文章说存在未提交的事务的情况下，在别的会话中也能在线添加字段不受影响的，但是我机器上测试还是会阻塞

有关ddl_time_out的设置，这个之前看过，没有注意过应用场景，参考：

https://orainternals.wordpress.com/2009/01/08/lock-table-followed-by-ddl/