Oracle RAC Transaction Locks Test

A transaction lock held for too long a time will prevent other sessions from accessing the database object, thereby stalling critical database operations. It is hence imperative to monitor the transaction locks to each database instance in an Oracle RAC. Using the RAC Transaction Locks test, you can determine the number of transaction locks held by each database instance and the duration of these locks, so that you can quickly identify the instance holding a large number of transaction locks and that which is holding locks for an unreasonably long time.

Target of the test : Oracle RAC

Agent deploying the test : An internal/remote agent

Outputs of the test : One set of results for each instance of 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.
  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

Number of Locks:

Indicates the number of locks held by this instance.

Number

A high value may indicate one of the following:

  • Too many transactions happening
  • Locked resources not being released properly
  • Locks are being held unnecessarily.

Average wait time:

Indicates the time for which the locks were held by this instance.

Seconds

A high value may indicate one of the following:

  • Too many transactions happening
  • Locked resources not being released properly
  • Locks are being held unnecessarily.