eG Monitoring
 

Measures reported by OraFlashAreaTest

The Flash Recovery Area is a specific area of disk storage that is set aside exclusively for retention of backup components such as datafile image copies, archived redo logs, and control file autobackup copies. These features include:

  • Unified Backup Files Storage. All backup components can be stored in one consolidated spot. The Flash Recovery Area is managed via Oracle Managed Files (OMF), and it can utilize disk resources managed by Oracle Automated Storage Management (ASM). In addition, the Flash Recovery Area can be configured for use by multiple database instances if so desired.
  • Automated Disk-Based Backup and Recovery. Once the Flash Recovery Area is configured, all backup components (datafile image copies, archived redo logs, and so on) are managed automatically by Oracle.
  • Automatic Deletion of Backup Components. Once backup components have been successfully created, RMAN can be configured to automatically clean up files that are no longer needed (thus reducing risk of insufficient disk space for backups).
  • Disk Cache for Tape Copies. Finally, if your disaster recovery plan involves backing up to alternate media, the Flash Recovery Area can act as a disk cache area for those backup components that are eventually copied to tape.
  • Flashback Logs. The Flash Recovery Area is also used to store and manage flashback logs, which are used during Flashback Backup operations to quickly restore a database to a prior desired state.

Oracle recommends that the Flash Recovery Area should be sized large enough to include all files required for backup and recovery. Using the OraFlashAreaUsage test, administrators can figure out whether the Flash Recovery Area is adequately sized or not, and accordingly make sizing recommendations.

Note:

For this test to work, the eG install user should be in the Oracle User Group.

The measures made by this test are as follows:

Measurement Description Measurement Unit Interpretation
Used_space Indicates the space currently occupied by the flash recovery files. MB  
Max_size_configured Indicates the maximum space allocated for flash recovery files. MB  
Pct_used Indicates the percentage of space occupied by the flash recovery files. Percent Oracle recommends that the Flash Recovery Area should be sized large enough to include all files required for backup and recovery. Therefore, ideally, the value of this measure should be very low. A value close to 100% indicates excessive usage of the recovery area; this implies that the flash recovery area could soon run out of space. in such a case you can resize the flash recovery area by reconfiguring the parameter "db_recovery_file_dest_size" in database parameter file, provided enough disk space is available. If not, then Oracle recommends that the flash area be sized at least large enough to contain any archived redo logs that have not yet been backed up to alternate media. Alternatively, you can remove the old files from the flash recovery area to create space for the new recovery files.

Pct_free Indicates the free space currently available for recovery files. MB  
Pct_free_diskspace Indicates the percentage of disk space that is currently available for use. Percent Disk space is a key factor in sizing the flash recovery area. The value to be set for the db_recovery_file_dest_size parameter should be decided after carefully considering the total disk space that is available for use. If the disk space is low, then Oracle recommends that the flash area be sized at least large enough to contain any archived redo logs that have not yet been backed up to alternate media. If very little disk space is free, then it would make more sense to free up some space in the disk or in the flash recovery area by removing old, unused files, so that enough space is available for the future files.