Oracle RAC Undo Usage Test

This test periodically monitors the space usage of UNDO tablespace of each instance managed by the Oracle cluster, and proactively alerts administrators to excessive space consumption by, or deficiencies in space allocations to, the UNDO tablespace.

Target of the test : Oracle RAC

Agent deploying the test : An internal/remote agent

Outputs of the test : One set of results for the undo tablespace of each instance managed by the monitored Oracle RAC

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 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.
Measurements made by the test
Measurement Description Measurement Unit Interpretation

Total space

Indicates the total size of the UNDO tablespace.

MB

 

Used space

Indicates the used size of the UNDO tablespace.

MB

 

Free space

Indicates the free size of the UNDO tablespace.

MB

Ideally, the value of this measurement should be very high.

Used percentage

Indicates the percentage of space allocated to the UNDO tablespace, which is already used.

Percent

Typically, a high percentage indicates that the available free space in this undo tablespace is very less. Therefore, to optimize this measure, the administrator is required to allocate sufficient space to this tablespace or tune the undo retention period and figure out the process that takes longer time to query the required data.