Oracle Extents Test

An extent in Oracle is a set of contiguous blocks allocated in Oracle for storage of data. Since this is one of the basic units of allocation, proper management of extents is essential for efficient database performance. The Oracle Extents test helps in identifying objects that are running out of extents and those that are using too many extents.

This test is disabled by default. To enable the test, go to the enable / disable tests page using the menu sequence : Agents -> Tests -> Enable/Disable, pick Oracle Database as the Component type, Performance as the Test type, choose this test from the disabled tests list, and click on the << button to move the test to the ENABLED TESTS list. Finally, click the Update button.

Note:

This test is applicable only for Oracle databases with ‘Dictionary Managed Tablespace’. From Oracle 9i onwards, all tablespaces are ‘Locally Managed Tablespaces’. Therefore, this test is applicable only up to Oracle 8i. 

Target of the test : An Oracle 12c server

Agent deploying the test : An internal agent

Outputs of the test : One set of results for every Oracle server.

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. MAXEXTENT - This test reports a Large extent objects measure, which reveals the number of objects that exceed a pre-configured number of extents; this limit is set using the MAXEXTENT parameter. If you enter a number in the MAXEXTENT text box, then, the Large extent objects measure of this test will return the count of objects with more extents than the number specified in the MAXEXTENT text box. By default, the MAXEXTENT parameter is set to 1000.

  8. alternate view – In large environments, where the volume of transactions to the Oracle database server is generally very high, this test may take time to execute and retrieve the desired results. To ensure that the test is faster and is resource-efficient, administrators of such environments can create an alternate ‘view’ on the target Oracle database server, and grant select privileges to the view to the special database user mentioned above. Once the view is created, the test should be configured to use the alternate view for metrics collection; to achieve this, specify the name of the view in the alternate view text box. By default, this text box is set to none, which implies that the alternate view is not used by default.

    This alternate ‘view’ should be created with the following structure:

    CREATE OR REPLACE VIEW <VIEW_NAME> (
    TABLESPACE_NAME,
    FILE_ID,
    BLOCK_ID,
    BYTES,
    BLOCKS,
    RELATIVE_FNO
    ) AS
    select /*+ use_hash (tsfi, fet2) */ tsfi.tablespace_name,
           tsfi.file_id,
           fet2.block_id,
           tsfi.blocksize * fet2.blocks,
           fet2.blocks,
           tsfi.relfile#
    from   (select /*+ use_hash (ts, fi) */ ts.name tablespace_name,
                   fi.file# file_id,
                   ts.BLOCKSIZE,
                   fi.relfile#,
                   ts.ts#
            from   sys.ts$ ts,
                   sys.file$ fi
            where  ts.ts# = fi.ts#
            and    ts.online$ in (1,4)) Tsfi,
           (select f.block# block_id,
                   f.length blocks,
                   f.file# file_id,
                   f.ts#
            from   sys.fet$ f
            union all
            select f.ktfbfebno block_id,
                   f.ktfbfeblks blocks,
                   f.ktfbfefno,
                   ktfbfetsn
            from   sys.x$ktfbfe f) Fet2
    where  fet2.file_id = tsfi.relfile#
    and    fet2.ts# = tsfi.ts# ;

  1. 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.
  2. DETAILED DIAGNOSIS – To make diagnosis more efficient and accurate, the eG Enterprise embeds an optional detailed diagnostic capability. With this capability, the eG agents can be configured to run detailed, more elaborate tests as and when specific problems are detected. To enable the detailed diagnosis capability of this test for a particular server, choose the On option. To disable the capability, click on the Off option.

    The option to selectively enable/disable the detailed diagnosis capability will be available only if the following conditions are fulfilled:

    • The eG manager license should allow the detailed diagnosis capability
    • Both the normal and abnormal frequencies configured for the detailed diagnosis measures should not be 0.
Measurements made by the test
Measurement Description Measurement Unit Interpretation

Cannot extend objects:

This measure indicates the number of objects that cannot extend any further by acquiring new extents.

Number

This measure indicates the objects have run out of extents. This could be because the objects are either too fragmented or the number of extents allocated to them are too less. Consider modifying the “maxextents” parameter to rectify this. Alternately if fragmentation is the cause then, consider exporting and then dropping and re-importing the object.

The detailed diagnosis of the Cannot extend objects measure, if available, provides a complete list of objects that cannot be extended. Once the objects are identified, administrators can then consider increasing the extents allocated to the listed objects.

Large extent objects:

This measure indicates the object that exceeds a pre-specified number of extents. The threshold value for the number of extents is configured via the admin user interface.

Number

This indicates that the objects are using up more extents than the threshold set. This over-utilization can be due to different types of fragmentation. Consider exporting and then dropping and re-importing the object. Note that the storage parameters set also affects how the extents are allocated.

The detailed diagnosis of the Large extent objects measure reveals the list of objects that exceed a pre-specified number of extents.