讲解V$Datafile_Header相关字段的使用

V$Datafile_Header相关字段的使用：

◆1、FUZZY也是用于表示数据文件 status的一个选项。

◆2、checkpoint_time用于查看何时发生了检查点，可用于判断一个操作是否会发出检查点。

在v9.0.1及之前的版本,FUZZY可以用于标识数据文件是不是处于hot backup状态。

当一个数据文件begin backup 时,fuzzy列即为yes,当end backup时这一列又被置为null

在9.2之后的版本，当数据库打开后，fuzzy这一列便为yes了

当数据文件为read write状态且为online时，则fuzzy列为yes

当数据文件为read only，则fuzzy为no

当数据文件为offline，则fuzzy为null

SQL> select * from v$version;

BANNER

----------------------------------------------------------------

Oracle9i Release 9.2.0.1.0 - PRoduction

PL/SQL Release 9.2.0.1.0 - Production

CORE 9.2.0.1.0 Production

TNS for 32-bit Windows: Version 9.2.0.1.0 - Production

NLSRTL Version 9.2.0.1.0 - Production

SQL> select * from v$tablespace;

TS# NAME INC

---------- ------------------------------ ---

0 SYSTEM YES

1 UNDOTBS1 YES

2 TEMP YES

3 INDX YES

4 TOOLS YES

5 USERS YES

6 CATTBS YES

已选择7行。

SQL> select status,fuzzy,tablespace_name,name from v$datafile_header;

STATUS FUZ TABLESPACE_NAME NAME

------- --- ------------------------------ -----------------------------------

ONLINE YES SYSTEM E:ORACLEORADATARCATSYSTEM01.DBF

ONLINE YES UNDOTBS1 E:ORACLEORADATARCATUNDOTBS01.DBF

ONLINE YES INDX E:ORACLEORADATARCATINDX01.DBF

ONLINE YES TOOLS E:ORACLEORADATARCATTOOLS01.DBF

ONLINE YES USERS E:ORACLEORADATARCATUSERS01.DBF

ONLINE YES CATTBS E:ORACLEORADATARCATCATTBS01.DBF

已选择6行。

SQL> alter tablespace users read only;

表空间已更改。

SQL> select status,fuzzy,tablespace_name,name from v$datafile_header;

STATUS FUZ TABLESPACE_NAME NAME

------- --- ------------------------------ -----------------------------------

ONLINE YES SYSTEM E:ORACLEORADATARCATSYSTEM01.DBF

ONLINE YES UNDOTBS1 E:ORACLEORADATARCATUNDOTBS01.DBF

ONLINE YES INDX E:ORACLEORADATARCATINDX01.DBF

ONLINE YES TOOLS E:ORACLEORADATARCATTOOLS01.DBF

ONLINE NO USERS E:ORACLEORADATARCATUSERS01.DBF

ONLINE YES CATTBS E:ORACLEORADATARCATCATTBS01.DBF

已选择6行。

SQL> alter tablespace users read write;

表空间已更改。

SQL> select status,fuzzy,tablespace_name,name from v$datafile_header;

STATUS FUZ TABLESPACE_NAME NAME

------- --- ------------------------------ -----------------------------------

ONLINE YES SYSTEM E:ORACLEORADATARCATSYSTEM01.DBF

ONLINE YES UNDOTBS1 E:ORACLEORADATARCATUNDOTBS01.DBF

ONLINE YES INDX E:ORACLEORADATARCATINDX01.DBF

ONLINE YES TOOLS E:ORACLEORADATARCATTOOLS01.DBF

ONLINE YES USERS E:ORACLEORADATARCATUSERS01.DBF

ONLINE YES CATTBS E:ORACLEORADATARCATCATTBS01.DBF

已选择6行。

SQL> alter tablespace users offline;

表空间已更改。

SQL> select status,fuzzy,tablespace_name,name from v$datafile_header;

STATUS FUZ TABLESPACE_NAME NAME

------- --- ------------------------------ --------------------------------

ONLINE YES SYSTEM E:ORACLEORADATARCATSYSTEM01.DBF

ONLINE YES UNDOTBS1 E:ORACLEORADATARCATUNDOTBS01.DBF

ONLINE YES INDX E:ORACLEORADATARCATINDX01.DBF

ONLINE YES TOOLS E:ORACLEORADATARCATTOOLS01.DBF

OFFLINE

ONLINE YES CATTBS E:ORACLEORADATARCATCATTBS01.DBF

已选择6行。

SQL> alter tablespace users online;

表空间已更改。

SQL> select status,fuzzy,tablespace_name,name from v$datafile_header;

STATUS FUZ TABLESPACE_NAME NAME

------- --- ------------------------------ ----------------------------------

ONLINE YES SYSTEM E:ORACLEORADATARCATSYSTEM01.DBF

ONLINE YES UNDOTBS1 E:ORACLEORADATARCATUNDOTBS01.DBF

ONLINE YES INDX E:ORACLEORADATARCATINDX01.DBF

ONLINE YES TOOLS E:ORACLEORADATARCATTOOLS01.DBF

ONLINE YES USERS E:ORACLEORADATARCATUSERS01.DBF

ONLINE YES CATTBS E:ORACLEORADATARCATCATTBS01.DBF

已选择6行。

通过checkpoint_time字段，可以判断是否发生检查点

SQL> alter session set nls_date_format='YYYY-MM-DD HH24:MI:SS';

会话已更改。

SQL> select status,fuzzy,tablespace_name,checkpoint_time from v$datafile_header;

STATUS FUZ TABLESPACE_NAME CHECKPOINT_TIME

------- --- ------------------------------ -------------------

ONLINE YES SYSTEM 2008-02-28 08:34:20

ONLINE YES UNDOTBS1 2008-02-28 08:34:20

ONLINE YES INDX 2008-02-28 08:34:20

ONLINE YES TOOLS 2008-02-28 08:34:20

ONLINE YES USERS 2008-02-28 10:07:28

ONLINE YES CATTBS 2008-02-28 08:34:20

已选择6行。

SQL> alter system suspend;

系统已更改。

SQL> alter system resume;

系统已更改。

SQL> select status,fuzzy,tablespace_name,checkpoint_time from v$datafile_header;

STATUS FUZ TABLESPACE_NAME CHECKPOINT_TIME

------- --- ------------------------------ -------------------

ONLINE YES SYSTEM 2008-02-28 08:34:20

ONLINE YES UNDOTBS1 2008-02-28 08:34:20

ONLINE YES INDX 2008-02-28 08:34:20

ONLINE YES TOOLS 2008-02-28 08:34:20

ONLINE YES USERS 2008-02-28 10:07:28

ONLINE YES CATTBS 2008-02-28 08:34:20

已选择6行。