UPDATE THE REPOSITORY

15. Update the repository:

Two-Minute Drill

Recover from a Lost TEMP File

• A temporary tablespace cannot be placed in backup mode.

• Tempfiles would not usually be restored—it is quicker to drop and recreate

them.

Recover from a Lost Redo Log Group

• Damaged log file members, or entire groups, can be dropped and recreated,

or cleared (which comes down to the same thing).

• Online redo log files must not be backed up for an open backup, and they

need not be backed up for a closed backup—if the database is shut down

cleanly.

Recover from the Loss of a Password File

• As a rule, the password file need not be backed up. Keep a copy of the

command used to create it, and recreate if necessary.

Perform User-Managed Complete Database Recovery

• The SQL*Plus command is RECOVER DATAFILE (in open mode, unless the

datafile is critical) or RECOVER DATABASE (in mount mode only).

• The steps for complete recovery of a noncritical datafile are

Take the file offline.

Restore the file.

Recover the file.

Bring the file online.

• The steps for complete recovery of a critical datafile are

Mount the database.

Open the database.

Perform User-Managed Incomplete Database Recovery

• The options are

Until a specified time

Until an SCN

Until the cancel command is submitted at the recovery prompt

• The steps are

Restore all datafiles (and the controlfile if necessary).

Recover the database UNTIL . . . .

Open the database with RESETLOGS.

• If using RMAN, the repository must be updated with RESET DATABASE.

Perform User-Managed Backups

• In noarchivelog mode, a complete backup while the database is shut down is

the only option.

• In archive log mode, there are three steps to an open backup:

ALTER DATABASE BACKUP CONTROLFILE.

Archive the online redo logs.

Copy the datafiles, while their tablespace is in backup mode.

Identify the Need for Backup Mode

• In backup mode, datafiles can be safely copied.

• When backup mode is enabled:

The datafile header is frozen.

The tablespace is checkpointed.

The redo generation algorithm switches from change vectors to complete

blocks.

• An open backup may contain fractured blocks, but these can be replaced with

read-consistent blocks from the redo stream.

Back Up and Recover a Controlfile

P AR T III

• Unless the database is closed, the controlfile can only be backed up with the

ALTER DATABASE BACKUP CONTROLFILE command.

• The easiest way to recover from the loss of a controlfile copy is to use another

copy.

• A binary backup of the controlfile can be restored.

• A controlfile can be recreated with the CREATE CONTROLFILE command,

if all the relevant information regarding datafiles and online redo log files is

available.

Self Test