MaintainingRedoLogFiles文件材料.ppt

Taking a Tablespace Offline (continued) Using Console to Take a Tablespace Offline Launch the Console: % oemapp console Choose Launch Standalone Expand your working database from the Databases folder Expand Storage folder Expand the Tablespaces folder. Select the tablespace. In the Status region of the General tab, select Offline. Select the Mode from the drop-down menu. Click Apply. Note: You can also launch the Console from Windows NT Start menu The ALTER TABLESPACE...READ ONLY Command Making tablespaces read-only prevents further write operations on the data files in the tablespace. Therefore, the data files can reside on read-only media, such as CD-ROMs or write-once (WORM) drives. Read-only tablespaces eliminate the need to perform backups of large, static portions of a database. Use the SQL command ALTER TABLESPACE to change a tablespace to read-only or read-write: ALTER TABLESPACE tablespace READ [ONLY | WRITE] To create a read-only tablespace on a write-once device: 1. ALTER TABLESPACE...READ ONLY. 2. Use an operating system command to move the data files of the tablespace to the read- only device. 3. ALTER TABLESPACE...RENAME DATAFILE. Making Tablespaces Read-Only The ALTER TABLESPACE...READ ONLY command places the tablespace in a transitional read-only mode. In this transitional state, no further write operations can take place in the tablespace except for the rollback of existing transactions that previously modified blocks in the tablespace. After all of the existing transactions have been either committed or rolled back, the ALTER TABLESPACE...READ ONLY command completes, and the tablespace is placed in read-only mode. Obtaining Log Group and Member Information V$LOG The following query returns information about the online redo log file from the control file: SQL SELECT group#, sequence#, bytes, members, status 2 FROM v$log; GROUP# SEQUENCE# BYTES MEMBERS STATUS 1 688 1048576 1 CURRENT 2 689 1048576 1 INACTIVE 2 rows selected.