Introduction › How to Analyze and Lower DASD Costs › Reduce Idle Space in Over-allocated Data Sets

Reduce Idle Space in Over-allocated Data Sets

As a storage administrator, you want to reduce idle space in data sets to reduce your costs of excess wasted DASD space.

In this example we show you how to reduce idle space in physical sequential (PS) and partitioned (PO) data set organization groups.

Follow these steps:

1. Expand the Diagnostics & Investigations, Data Set Management, All directory in the Storage object tree in the Investigator, and open the Data Sets for System (All) object.
2. Create a filter to display PS data sets with a large amount of idle space and click Search.

   For example, create the following filter statement:

   % Idl >= 80 
   AND Dso = PS
   

   Note: The greater-than or equal-to 80 percent idle space is a suggested value. Use a filter value according to your policy. Sites can release idle space that is based on a lower or higher idle space percentage value.

   The table is updated and lists only the PS data sets containing idle space greater-than or equal-to 80 percent. If data sets do not appear, none meet the search criteria. Consider changing the percent idle space filter to a lower value. If data sets are listed and you want to release idle space, go to the next step.

3. Click the % Idle column header until the table rows are sorted by the % Idle column in descending order with the highest % idle listed at the top of the table.
4. Select the check box of the rows of the over-allocated data sets from which you want to release idle space.
5. Select Idle Space Release in the Administrative Actions section of the Actions pane.
6. Select the following options at the bottom of the Actions dialog to simulate the action:

   Note: We suggest that you first simulate the line action. When you are satisfied with the results, perform the real line action by selecting the Live Mode (Y,N) field.

   Live Mode (Y,N)

   Clear this check box to indicate N for simulate mode.

   Convert Tracks (Y,N)

   Select this check box to indicate Y, which indicates cylinder allocation attributes are converted to track allocations. Clear this check box to indicate N, which indicates cylinder allocation attributes are not converted to track allocations.

   Note: Consider if the data set receives many updates and a large amount of allocated space is needed. If that is the case, then you should probably not convert the cylinder allocation attributes to track allocations.

   Pct Idle After Space Release

   Specify the amount of idle space to remain in the data set after the release occurs, according to your policy.

7. Click Submit to simulate the storage engine line action.

   A simulated result of the action is displayed.

8. Choose one of the following options:
   • A Release message that includes the data set names is displayed when there is no error. If you do not have errors, you are ready to officially release the idle space. Go to step 12.
   • If an error occurs, a message is displayed indicating the error condition. If you have errors, go to step a.
     1. Do one of the following tasks to resolve the error:

        - Unselect the error items in the Investigator so they are not included in the line action.

        - Change the Pct Idle After Space Release value to a lower value.

     2. Click Submit to simulate the line action again.
     3. If error messages persist, repeat steps a and b until no error messages appear.
9. Select the Live Mode (Y,N) check box to indicate that you want to perform the action.
10. Click Submit to release space.

    Idle space is released according to your specifications. The idle space values that you specified for Pct Idle After Space Release remains in the data sets.

11. Release space from PO data sets by repeating steps 2 through 10. Change the filter in step 2 to display PO data sets. The following filter statement is how the new filter looks:

    % Idl >= 80 
    AND Dso = PO 
    

    You have identified the PO data sets with idle space above your policy and released idle space from them.

12. (Optional) Click the notes icon in the Investigator tool bar, and add a note to the items for which you reduced idle space to indicate what you did and when.
13. (Optional) Repeat the cost analysis of your DASD to see if you need to release additional idle space.

    Your DASD costs are within your target limits. You have reduced unused over-allocated space in your DASD so it is available for use. These changes let you reduce or defer the cost of adding new DASD to your site.