Managing Archived Redo Logs

By Kamran Agayev A.

The LOG_ARCHIVE_MAX_PROCESSES parameter specifies the number of ARCn processes that the database initially invokes. The default is two processes. You can specify this parameter up to ten processes to be started at instance startup. It is dynamic parameter and can be changed with ALTER SYSTEM command. The database must be mounted, but not opened.

If you want to archive only to a single destination, you specify that destination in the LOG_ARCHIVE_DEST parameter. If you want to multiplex the archived logs, you can choose whether to archive to up to ten locations (using the LOG_ARCHIVE_DEST_n parameters) or to archive to a primary and secondary destinations (LOG_ARCHIVE_DEST and LOG_ARCHIVE_DUPLEX_DEST)

You specify the location for LOG_ARCHIVE_DEST_n using the keywords LOCATION (for a local file system) and SERVICE (remote archival through Oracle Net service name):

LOG_ARCHIVE_DEST_1=’LOCATION=/disk1/archive’;

LOG_ARCHIVE_DEST_2=’SERVICE=standby’;

The optional parameter LOG_ARCHIVE_MIN_SUCCEED_DEST=n determines the minimum number of destinations to which the database must successfully archive a redo log group before it can reuse online log files. the default value is 1. Valid values for n are 1 to 2 if you are using dupliexing, or 1 to 10 if you are multiplexing.

MANDATORY option specifies that the transmission of the redo data to the destination must succeed before the local online redo log file can be made available for reuse. The default is OPTIONAL.

REOPEN option specifies the minimum number of seconds before the archived process (ARC) or the LGWR should try again to access a previously failed destination. Default is 300 seconds.

VERIFY option indicates if an archived (ARC) process should scan and verify the correctness of the contents of the completed archived redo log file, either local or remote, after successfully completing the archival operation. By default, archived redo log file are not verified.

When you specify REOPEN for an OPTIONAL destination, the database can overwrite online logs if ther is an error. If you specify REOPEN for a MANDATORY destination, the database stalls the production database when it cannot successfully archive.

Use LOG_ARCHIVE_TRACE parameter to specify a trace level

To get information about archived redo logs use the following views:

• V$ARCHIVED_LOG

• V$ARCHIVE_DEST

• V$ARCHIVE_PROCESSES

• V$BACKUP_REDOLOG

• V$LOG

• V$LOG_HISTORY