Using the above log files and backup files, DB2 UDB can support database 

recovery by various methods and to

different levels:

Crash/restart recovery

This is a technique for an automated database recovery to recover the 

database to a stage where all the transactions are completed and committed. 

This is done by rolling back incomplete transactions and completing 

committed transactions that were still in memory when the crash occurred.

This is done automatically by the database manager if you set the automatic 

restart (autorestart) database configuration parameter to 

ON

 by:

db2>db2 update database configuration for itsodb2 using autorestart ON

or by restarting the database when a database failure occurs; this is done by 

calling:

db2>restart database itsodb2

DB2 UDB maintains log files, the recovery history file, and table space 

change history file to recover data that is lost or damaged.

Version recovery

This is recovery option used for non recoverable databases or databases 

without achieved logs. In this recovery option, previous backup versions of 

the database are restored in case of an emergency. Typically, database 

backups are taken in tapes and kept in remote places. 

It is very necessary to take a backup on regular basis because this recovery 

method loses the changes made in database after backup. This is done by 

restoring the database using incremental, delta, or full backup.

Rollforward recovery 

In rollforward recovery, you can specify the local time to which you want to roll 

forward your database. In this method backup data is used in conjugation with 

database transaction records to achieve a goal of taking DB2 UDB to the 

state immediately before the failure. Figure 8 2 shows the roll forward 

recovery technique of DB2 UDB.

 Chapter 8. Database administration 

239