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Table 5–1 describes potential problems that can occur during media recovery.

Table 5–1 Media Recovery Problems

Problem Description

Missing or misnamed archived log

Recovery stops because Oracle cannot find the archived log recorded in the control file.

When you attempt to open the database, error

ORA-1113 indicates that a file needs media recovery

This error commonly occurs because:

■ You are performing incomplete recovery but failed to restore all needed datafile backups.

■ Incomplete recovery stopped before datafiles reached a consistent SCN. ■ You are recovering datafiles from an online backup, but not enough redo

was applied to make the datafiles consistent.

■ You are performing recovery with a backup control file, and did not specify the location of a needed online log.

■ A datafile is undergoing media recovery when you attempt to open the database.

■ Datafiles needing recovery were not brought online before executing

RECOVER DATABASE, and so were not recovered. Redo record problems Two possible cases are as follows:

■ Recovery stops because of failed consistency checks, a problem called stuck

recovery. Stuck recovery can occur when an underlying operating system or

storage system loses a write issued by Oracle during normal operation of the database.

■ Oracle signals an internal error when applying the redo. This problem can be caused by an Oracle bug. If checksums are not being used, it can also be caused by corruptions to the redo or data blocks.

Corrupted archived logs Logs may be corrupted while they are stored on or copied between storage systems. IfDB_BLOCK_CHECKSUM is enabled, then Oracle usually signals checksum errors. If checksumming is not on, then log corruption may appear as a problem with redo.

The symptoms of media recovery problems are usually external or internal errors signaled during recovery. For example, an external error indicates that a redo block or a data block has failed checksum verification checks. Internal errors can be caused by either bugs in Oracle or errors arising from the underlying operating system and hardware.

If media recovery encounters a problem while recovering a database backup, whether it is a stuck recovery problem or a problem during redo application, Oracle always stops and leaves the datafiles undergoing recovery in a consistent state, that is, at an SCN preceding the failure. You can then do one of the following:

■ Open the database read-only to investigate the problem.

■ Open the database with theRESETLOGS option, as long as the requirements for

openingRESETLOGS have been met (as described in"Opening the Database After User-Managed Media Recovery" on page 4-26). Note that theRESETLOGS restrictions apply to opening the standby database as well, because a standby database is updated by a form of media recovery.

In general, opening the database read-only or opening with theRESETLOGS option require all online datafiles to be recovered to the same SCN. If this requirement is not met, then Oracle may signalORA-1113 or other errors when you attempt to open. Some common causes ofORA-1113 are described inTable 5–1.

The basic methodology for responding to media recovery problems occurs in the following phases:

1. Try to identify the cause of the problem. Run a trial recovery if needed. Archived logs with

incompatible parallel redo format

If you enable the parallel redo feature in Oracle9i Release 2 (9.2), then Oracle generates redo logs in a new format. Prior releases of Oracle are unable to apply parallel redo logs. However, Oracle9i Release 1 (9.0.1) can detect the parallel redo format and indicate the inconsistency with the following error message:

External error 00303, 00000, "cannot process Parallel Redo".

See Also: Oracle9i Database Performance Tuning Guide and Reference to learn about

the parallel redo feature

Corrupted data blocks A datafile backup may have contained a corrupted data block, or the data block may become corrupted either during recovery or when it was copied to the backup. If checksums are being used, then Oracle signals a checksum error. Otherwise, the problem may also appear as a redo corruption.

Random problems Memory corruptions and other transient problems can occur during recovery. Table 5–1 Media Recovery Problems (Cont.)

2. If the problem is related to missing logs or you suspect there is a log, memory, or data block corruption, then try to resolve it using the methods described in Table 5–2.

3. If you cannot resolve the problem using the methods described inTable 5–2, then do one of the following:

– Open the database with theRESETLOGS option if you are recovering a whole database backup. If you have performed serial media recovery, then the database contains all the changes up to but not including the changes at the SCN where the corruption occurred. No changes from this SCN onward are in the recovered part of the database. If you have restored online backups, openingRESETLOGSsucceeds only if you have recovered through all theALTER ... END BACKUP operations in the redo stream.

– Proceed with recovery by allowing media recovery to corrupt data blocks. After media recovery completes, try performing block media recovery using RMAN.

– Call Oracle Support Services as a last resort.