Oracle Rollbacks Test

The immediate availability of rollback segments for the various activities that occur in a database server is very critical. Contention for rollback segments can adversely impact the performance of a database server and hence, needs to be detected and reported immediately. To detect contention for rollback segments, the Oracle Rollbacks test monitors the degree of contention for buffers that contain rollback segment blocks.

Note:

This test will not report metrics for an Oracle 12c CDB 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

System segment waits:

Denotes the ratio of the number of waits for acquiring a header block or a block of the SYSTEM rollback segment to the total number of requests for data, measured over a period of time.

Percent

If the number of waits for any class of block exceeds 1% of the total number of requests, the size of the SYSTEM rollback segment needs to be increased.

Non-system segment waits:

Denotes the ratio of the number of waits for acquiring a header block or any other block of a non-SYSTEM rollback segment to the total number of requests for data, measured over a period of time.

Percent

If the number of waits for any class of block exceeds 1% of the total number of requests, the sizes of the existing rollback segments may need to be increased. Alternatively, additional rollback segments to may be created to reduce contention.