This section provides only a very brief overview of standard backup and recovery options. For more detailed information about backup and recovery options, refer to Chapter 10.
Even if you’ve taken adequate precautions, critical database records can sometimes be destroyed as a result of user error or hardware or software failure. The only way to prepare for this type of potentially disastrous situation is to perform regular backup operations.
Two basic types of potential failures can affect an Oracle database: instance failure, in which the Oracle instance terminates without going through the shutdown process; and media failure, in which the disks that store the information in an Oracle database are corrupted or damaged.
After an instance failure, Oracle will automatically perform crash recovery; you can use Real Application Clusters/Oracle Parallel Server to automatically perform instance recovery when one of its instances crashes. However, DBAs must initiate recovery from media failure. The ability to recover successfully from this type of failure is one of the greatest challenges a DBA faces—it’s also the place where the value of the DBA becomes most apparent! The recovery process includes restoring older copies of the damaged datafile(s) and rolling forward by applying archived and online redo logs.
To ensure successful recovery, the DBA should have prepared for this eventuality by performing the following actions:
Multiplexing online redo logs by having ...