eG Monitoring
 

Measures reported by OraArchiveAreaTest

An Oracle database can run in one of two modes. By default, the database is created in NOARCHIVELOG mode. When in NOARCHIVELOG mode the database runs normally, but there is no capacity to perform any type of point in time recovery operations or online backups. In ARCHIVELOG mode on the other hand, the database will make copies of all online redo logs after they are filled. These copies are called archived redo logs. The archived redo logs are created via the ARCH process. The ARCH process copies the archived redo log files to one or more archive log destination directories.

Note that while the database is being run in the ARCHIVELOG mode, then once an online redo log has been filled, it cannot be reused until it has been archived. If, in the meantime, the destination directory for the archived redo logs runs out of space, then Oracle cannot archive the online redo log. Instead, it will switch to the next online redo log and keep working, while continuing its efforts to archive the log file.

If the database is unable to archive the redo log files for a long time, then at some point it might run out of available online redo logs. Since it cannot reuse the unarchived redo logs for writing the new redo log entries, the database freezes all its operations and stops processing user requests until such time that space is freed in the archive log destination directories.

To ensure that the database is always available to process requests, administrators need to ensure that the archive log destination directories are adequately sized. The OraArchiveArea test periodically monitors the usage of the archive log destination directories, and warns administrators about a sudden/consistent decrease in the free space available in the directories. This enables administrators to act fast and free sufficient space in the directories, so as to prevent the database from suspending its activities.

Note:

For this test to work;

  • The eG install user should be in the Oracle User Group.

  • The database should run in ARCHIVELOG mode

The measures made by this test are as follows:

Measurement Description Measurement Unit Interpretation
Archive_area_used Indicates the space currently occupied by the archive files in the archive destination directory. MB  
Total_used_area Indicates the space in the archive destination drive that is currently occupied by all files, including archive files. MB  
Pct_archive_area_used Indicates the percentage of total used space in the archive destination drive, which is occupied by the archive files. Percent This measurement value should ideally be below 50%. Any value higher than 50%, indicates that the archive files are consuming more space than the other files in the archive destination drive. To free some space in that drive, you can adopt any of the following approaches:

  • Add more disk space to the archive drive;

  • Take backups of the old archive files to tape or to another destination, and remove them from the destination directory;

  • Temporarily, you can even zip all archive files in the archive destination.
Available Indicates the current free space in the archive destination. MB  
Pct_available Indicates the percentage of unused space in the archive destination. Percent This measurement value should ideally be high. If the value is consistently low, you may want to check the value of the Relative archive area usage measure to determine what is causing the space drain - is it because of the archive files, or the other files in the archive destination drive? If the archive files appear to be consuming excessive space in the drive, you can free some space in the drive by adopting any of the following approaches:

  • Add more disk space to the archive drive;

  • Take backups of the old archive files to tape or to another destination, and remove them from the destination directory;

  • Temporarily, you can even zip all archive files in the archive destination.
Archive_growth Indicates the rate at which the archive files occupy space in the archive destination directory during the last measurement period. MB/sec Ideally the value of this measure should be low. A high value indicates that there exists a space constraint in the archive destination directory and reveals that the I/O related activity is high in the directory.