A media error occurs when a read or write error takes place in a database file due to a physical defect on the disk drive where the file is located. The most frequent physical defect is a head crash, which usually renders all the files on a disk unusable.
In most cases, the database must be recovered after a media error. The recovery strategy depends on the type of damage in the database. You must therefore analyze the error and understand how it was caused before you can continue with the recovery.
If you are not sure how to perform a recovery, please contact your SAP consultant or an ORACLE specialist. Do NOT attempt to just "give it a try".
An incorrectly performed recovery can lead to irretrievable loss of data in your database. The damage you risk is much more costly than the time you spend on a carefully planned, properly executed recovery of your database.
In addition to the ALERT and trace files, SAP recommends using the SAPDBA Check function (Check (and repair) database ® Check database) to analyze the database. If defects in the data files of the database are involved, SAPDBA can often perform the database recovery automatically.
See SAPDBA Database Recovery.
This section is intended to provide an overview of the recovery process using ORACLE utilities. Use the ORACLE utility SVRMGR. The sections below contain examples of the command line operations with SVRMGR.
If you have followed the SAP recommendations regarding the installation and operation of the database system, you should generally succeed in carrying out a complete recovery after a media error. If, however, in an extreme case your backups of the database and your redo log archives have been damaged too, you may only be able to carry out an incomplete recovery.
The procedures required for the following errors are listed in the following:
- Loss of one or all copies of the control file
- Loss of an online or offline redo log file or even an entire online redo log group
- Loss of a system, temporary, user, or index tablespace
- Error in the archiving process for online redo log files using ARCH
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