Entering content frameProcedure documentation Mirroring Online Redo Log Files Locate the document in its SAP Library structure

Use

It is essential to mirror the online redo log files in your Oracle database.

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

This procedure describes how to check the mirroring with SAPDBA.

  1. During SAPDBA startup, any missing online redo log files are displayed if the profile parameters check_initial_settings or check_redolog_mirror are configured properly.
    See     check_initial_settings
  2. Choose Archive mode ® Show all archive information: ONLINE REDO LOGS in SAPDBA. Refer to Setting Archive and Database Mode with SAPDBA.
  3. When the database is open, you can also check the mirroring with the Oracle program SQLPLUS:

    4. SQLPLUS> connect internal
    SQLPLUS> select * from V$logfile;

  4. You can also make additional mirror copies. For more information, see the appropriate Oracle documentation. In addition, many systems support hardware-based file mirroring. For more information, see your operating system documentation.

For more information on the security of offline redo log files, see Backup of the Offline Redo Log Files.

Leaving content frame