Oracle Rollback Segments Test

Rollback segments are the undo records, which contain the picture before the database changes. These segments are a critical part of the recovery process and are applied during the rollback phase of the recovery process. The Oracle Rollback Segments test measures the load and the efficiency of the rollback segments.

Note:

This test will not report metrics for an Oracle 12c PDB server.

Target of the test : An Oracle server

Agent deploying the test : An internal agent

Outputs of the test : One set of results for every SID monitored.

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. 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.

  5. Password – Password of the specified database user

    This login information is required to query Oracle’s internal dynamic views, so as to fetch the current status / health of the various database components.

  6. Confirm password – Confirm the password by retyping it here.
  7. 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

Writes:

Indicates the total number of writes to a specific rollback segment during the last measurement period.

Number

This gives you an indication of the load on a specific rollback segment.

Waits:

Indicates the number of header waits during the last measurement period.

Number

This indicates the number of times the Oracle Server had to wait to acquire a rollback segment.

Gets:

Indicates the number of header gets during the last measurement period.

Number

This indicates the number of gets that have happened in a specific rollback segment.

Current hit ratio:

Indicates the waits to gets ratio during the last measurement period.

Percentage

This indicates the efficiency at which the rollback segments have performed during the last monitored interval. Ideally, the Hit Ratio should be >= 99%.

Overall hit ratio:

Indicates the waits to gets ratio from the time the instance was started

Percentage

Ideally, the Hit Ratio should be >= 99%. If not, consider adding additional rollback segments. Also, check the system undo header, system undo block, undo header, undo block statistics under “Wait Statistics”, for additional information on rollback contention.