一 offline 表空间注意事项
不能离线如下表空间
system
undo tablespace
temporary tablespace
二、 alter tablespace …offline 后面可跟参数 normal/temporary/immediate
normal:
A tablespace can be taken offline normally if no error conditions exist
for any of the datafiles of the tablespace. No datafile in the tablespace
can be currently offline as the result of a write error. When you specify
OFFLINE NORMAL, the database takes a checkpoint for all datafiles of the
tablespace as it takes them offline. NORMAL is the default
以上说明：
1 normal 是offline的默认方式
2 normal 对表空间的所有数据文件执行检查点操作，online表空间时不需要介质恢复。
3 normal 方式离线表空间时，不应该有写错误，表空间所有文件应该online状态。
temporary:
A tablespace can be taken offline temporarily, even if there are
error conditions for one or more files of the tablespace. When
you specify OFFLINE TEMPORARY, the database takes offline the
datafiles that are not already offline, checkpointing them as it
does so.
If no files are offline, but you use the temporary clause, media
recovery is not required to bring the tablespace back online.
However, if one or more files of the tablespace are offline
because of write errors, and you take the tablespace offline
temporarily, the tablespace requires recovery before you can
bring it back online.
以上说明：
1 offline temporary 表空间时，如果表空间中没有offline的数据文件，则online该表空间时不需要介质恢复。
2 offline temporary 表空间时，不会对已经offline的数据文件执行检查点操作，仅仅对online的数据文件执行检查点操作
3 offline temporary 表空间时，对于离线表空间之前已经offline的数据文件，则online该表空间时，offline数据文件需要介质恢复。
immediate:
A tablespace can be taken offline immediately, without the
database taking a checkpoint on any of the datafiles. When you
specify OFFLINE IMMEDIATE, media recovery for the tablespace is
required before the tablespace can be brought online. You
cannot take a tablespace offline immediately if the database is
running in NOARCHIVELOG mode.
以上说明三点：
1 offline immediate 不会对表空间的任何文件执行检查点操作。
2 online 表空间时需要对所有数据文件进行 media recovery
3 offline immediate 需要数据库日志模式为归档
注意事项
如果必须离线表空间，推荐使用offline normal 方式离线该表空间，因为该表空间online时不需要执行介质恢复。
三 实验
1 测试offline temporary
查询系统当前表空间以及相应的数据文件
SQL> select a.name as tablespace,b.file#,b.status,b.name as datafile from v$tablespace a,v$datafile b where a.ts#=b.ts#;
TABLESPACE FILE# STATUS DATAFILE
------------------------------ ---------- ------- ------------------------------
SYSTEM 1 SYSTEM /oracle/CRM2/CRM/system01.dbf
SYSAUX 3 ONLINE /oracle/CRM2/CRM/sysaux01.dbf
USERS 4 ONLINE /oracle/CRM2/CRM/users01.dbf
UNDOTBS2 6 ONLINE /oracle/CRM2/CRM/undotbs2.dbf
ZX 5 ONLINE /oracle/CRM2/CRM/zx1.dbf
ZX 2 ONLINE /oracle/CRM2/CRM/zx2.dbf
SQL> alter database datafile 2 offline;
Database altered.
不能用offline normal正常offline 因为表空间zx数据文件2已经offline状态
SQL> alter tablespace zx offline;
alter tablespace zx offline
*
ERROR at line 1:
ORA-01191: file 2 is already offline - cannot do a normal offline
ORA-01110: data file 2: '/oracle/CRM2/CRM/zx2.dbf'
用offline temporary 离线
SQL> alter tablespace zx offline temporary;
Tablespace altered.
SQL> alter tablespace zx online;
alter tablespace zx online
*
ERROR at line 1:
ORA-01113: file 2 needs media recovery
ORA-01110: data file 2: '/oracle/CRM2/CRM/zx2.dbf'
SQL> recover datafile 2;
Media recovery complete.
使zx表空间online
SQL> alter tablespace zx online;
Tablespace altered.
2 测试offline immediate
查询当前表空间及其数据文件。
SQL> select a.name as tablespace,b.file#,b.status,b.name as datafile from v$tablespace a,v$datafile b where a.ts#=b.ts#;
TABLESPACE FILE# STATUS DATAFILE
------------------------------ ---------- ------- ------------------------------
SYSTEM 1 SYSTEM /oracle/CRM2/CRM/system01.dbf
SYSAUX 3 ONLINE /oracle/CRM2/CRM/sysaux01.dbf
USERS 4 ONLINE /oracle/CRM2/CRM/users01.dbf
UNDOTBS2 6 ONLINE /oracle/CRM2/CRM/undotbs2.dbf
ZX 5 ONLINE /oracle/CRM2/CRM/zx1.dbf
ZX 2 ONLINE /oracle/CRM2/CRM/zx2.dbf
SQL> alter tablespace zx offline immediate;
Tablespace altered.
SQL> alter tablespace zx online;
alter tablespace zx online
*
ERROR at line 1:
ORA-01113: file 2 needs media recovery
ORA-01110: data file 2: '/oracle/CRM2/CRM/zx2.dbf'
SQL> recover datafile 2;
Media recovery complete.
SQL> alter tablespace zx online;
alter tablespace zx online
*
ERROR at line 1:
ORA-01113: file 5 needs media recovery
ORA-01110: data file 5: '/oracle/CRM2/CRM/zx1.dbf'
SQL> recover datafile 5;
Media recovery complete.
SQL> alter tablespace zx online;
Tablespace altered.