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Mirroring the Online Redo Log FilesLocate this document in the navigation structure

Use

It is essential to mirror the online redo log files in your Oracle database. This procedure describes how you can check the mirroring with BRSPACE. Also, the system check in BRCONNECT checks mirroring.

If you lose one or more online redo log files, you can no longer recover the database changes recorded in them. This means that you can only recover the database up to the first gap in the online redo log records. For this reason, we strongly recommend that you mirror the online redo log files. We recommend that you make at least one copy.

If an online redo log file of a group is lost, the database remains in operation. Oracle then uses the remaining member (or members) of this group to log the database changes. In such a case, you must recover the original mirroring of the online redo log files as quickly as possible.

For more information see:

Prerequisites

When an SAP System is installed using Oracle resources, an online redo log group normally consists of the original online redo log file and a mirror copy of this file (that is, the group has two members).

Procedure

  1. Do one of the following to check mirroring:

    • Choose Start of the navigation path Space management Next navigation step Additional space functions Next navigation step Show redo log files End of the navigation path in BRGUI or BRTOOLS.

    • Enter brspace -f dbshow -c rfinfo from the command line.

    • Call the Oracle program SQLPLUS:

      SQL> connect / as sysdba

      SQL> select * from v$logfile;

    • Run the database system check with BRCONNECT. The condition to check mirroring of the online redo log files is REDOLOG_FILE_MIRROR. For more information, see BRCONNECT Default Conditions for Database Administration.

  2. You can make additional mirror copies using the BRSPACE function moredo with action crmember for each online redo log group by entering the following command:

    brspace -f moredo -a crmember

For more information on the security of offline redo log files, see Backing Up the Offline Redo Log Files with BR*Tools.