Oracle RAC Flash Area Usage Test

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 this test, administrators can figure out whether the Flash Recovery Area is adequately sized or not, and accordingly make sizing recommendations.

Note:

This test is applicable only to clusters based on Oracle database server 10g (and above).

Target of the test : An Oracle database server 10g

Agent deploying the test : An internal agent

Outputs of the test : One set of results for the flash recovery area on each node in the Oracle cluster

Configurable parameters for the test
  1. TEST PERIOD - How often should the test be executed
  2. Host – The host for which the test is to be configured
  3. Port - The port on which the server is listening
  4. orasid - The variable name of the oracle instance
  5. service name - A ServiceName exists for the entire Oracle RAC system. When clients connect to an Oracle cluster using the ServiceName, then the cluster routes the request to any available database instance in the cluster. By default, the service name is set to none. In this case, the test connects to the cluster using the orasid and pulls out the metrics from that database instance which corresponds to that orasid. If a valid service name is specified instead, then, the test will connect to the cluster using that service name, and will be able to pull out metrics from any available database instance in the cluster.

    To know the ServiceName of a cluster, execute the following query on any node in the target cluster:

    select name, value from v$parameter where name =’service_names’

  6. User – In order to monitor an Oracle RAC, a special database user account has to be User – In order to monitor an Oracle database server, a special database user account has to be created in every Oracle database instance that requires monitoring. A Click here hyperlink is available in the test configuration page, using which a new oracle database user can be created. Alternatively, you can manually create the special database user. When doing so, ensure that this user is vested with the select_catalog_role and create session privileges.

    The sample script we recommend for user creation (in Oracle database server versions before 12c) for eG monitoring is:

    create user oraeg identified by oraeg create role oratest;

    grant create session to oratest;

    grant select_catalog_role to oratest;

    grant oratest to oraeg;

    The sample script we recommend for user creation (in Oracle database server 12c) for eG monitoring is:

    alter session set container=<Oracle_service_name>;

    create user <user_name>identified by <user_password> container=current default tablespace <name_of_default_tablespace> temporary tablespace <name_of_temporary_tablespace>;

    Grant create session to <user_name>;                                 

    Grant select_catalog_role to <user_name>;

    The name of this user has to be specified here.

  7. Password – Password of the specified database user
  8. Confirm password – Confirm the password by retyping it here.
  9. ISPASSIVE – If the value chosen is yes, then the Oracle server under consideration is a passive server in an Oracle cluster. No alerts will be generated if the server is not running. Measures will be reported as “Not applicable’ by the agent if the server is not up.
Measurements made by the test
Measurement Description Measurement Unit Interpretation

Used flash area:

Indicates the space currently occupied by the flash recovery files on this node.

 

MB

 

Maximum flash area size:

Indicates the maximum space allocated for flash recovery files on this node.

MB

 

 

Flash area usage: 

Indicates the percentage of space occupied by the flash recovery files on this node.

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.

Free flash area:

Indicates the free space currently available for recovery files on this node.

Percentage