Step 3: Assigning objects to buffer pools

Follow the procedure to assign objects to buffer pools.

About this task

When you have performed Step 2: Editing a pattern file, the third page of the object placement wizard is displayed:
Figure 1. Object Placement – The Object Assignment window
This figure is a graphical representation of the Object Assignment window from an object placement.
This page shows the object placements that Buffer Pool Analyzer recommends based on the previously specified placement rules.
  • Buffer Pool Analyzer has scanned the bpd file and has analyzed the characteristics of each table space and index space.
  • The Current column shows the placement of objects at the time the data was collected.
  • The Recommended column shows the recommended object to buffer pool assignments, as calculated by Buffer Pool Analyzer. The calculations are based on the placement rules for each buffer pool and the object's characteristics.
  • The User-defined column is initially identical with the Recommended column, and is intended to change assignments as described later in this topic.
You can use this page to change the object placements, which means, you can assign specific objects to buffer pools other than the ones determined by the placement rules. You might want to do this, for example, to assign certain objects to a particular large buffer pool to guarantee high performance for applications using these objects. These user-defined assignments overwrite the assignments recommended by Buffer Pool Analyzer.
  • To change the assignment of an object, double-click the appropriate buffer pool name in the User-defined column and edit the buffer pool name. Then press Enter or select a different field.
  • To reset a User-defined assignment of an object to the Recommended assignment, select the object and click Reset selected.

    You can reset multiple assignments by selecting multiple objects. To select a range of successive objects, click the first object, hold down the Shift key, then click the last object in the sequence. To select several separate objects, click the first object, hold down the Ctrl key, then click the other objects as required. To select all objects, press Ctrl+A.

The following list describes the elements of an assignment, as shown on the page. Note that you can sort the list by clicking a column header of choice one or more times. Small arrows indicate the sort order.
Object Name
Shows the name of an object, such as a table space or index space. If you selected the Assign objects not accessed during data collection checkbox on the previous page, this column also shows the names of unused objects. Note that unused (inactive) objects can be explicitly excluded from bpd files. If such bpd file was opened, the use of the checkbox has no effect.
Type
Shows the type of an object, as TABLESPACE, INDEX, LOB, TEMP, or WORK/SORT.
Page
Shows the page size of the buffer pool to which an object is currently assigned. If you assign an object to a different buffer pool, the new buffer pool must have the same page size.
Used
Shows whether an object was used during the time for which performance data was collected.

If an object was used (indicated as YES), Buffer Pool Analyzer assigned the object to a buffer pool according to the object's characteristics.

If an object was not used (indicated by NO), Buffer Pool Analyzer retains the original assignment, unless you checked the Assign objects not accessed during data collection checkbox on the previous page. In this case, Buffer Pool Analyzer assigned the object using only the object's Page Size, Size, and data type (Data, Index, LOB, or Sort/Temp).

Catalog/Directory
Shows whether this object is part of the database catalog (CAT) or database directory (DIR). No entry indicates that the object belongs to neither.
Seq. Access [%]
Shows how often the object was accessed sequentially, as a percentage of all accesses to this object.

N/C (not calculated) means that the percentage could not be computed because the object was not used.

Change Rate [%]
Shows how often the object was changed, as a percentage of all accesses to this object.

N/C (not calculated) means that the percentage could not be computed because the object was not used.

Size [pages]
Shows the size of an object, expressed as the number of buffer pool pages.

Example: For a buffer pool having a page size of 4 KB, a value of 12 corresponds to an object size of 48 KB.

Current
Shows the name of the buffer pool where an object is currently placed (at the time the data was collected).
Recommended
Shows the name of the buffer pool that Buffer Pool Analyzer recommends for the object.
User-defined
Initially, this column shows the same buffer pool names as in the Recommended column.
Note: If a field in this column is empty, an object was not assigned to a buffer pool because no matching rule was found. You must ensure that there are no empty user-defined fields before continuing. Return to Step 2: Editing a pattern file and add rules that cover such objects.

If you want to assign objects to specific buffer pools (other than those shown in the corresponding fields), you can change the assignment in this column as described previously.

You can also reset your changes to the recommended values by clicking Reset selected or Reset all. The latter resets the assignments of all objects in the window, but not those that are hidden if the Show only objects with activity checkbox is selected. If you want to reset all used and unused objects, clear the checkbox (which shows used and unused objects in the window), click Reset all, then select the checkbox again.

Restriction: Catalog objects and directory objects cannot be assigned to different buffer pools.

Procedure

  1. Review the assignments on this page. Change them in the User-defined column, if required.
  2. Use the Show only objects with activity checkbox to indicate whether you want to see only used objects, or whether you want to see also unused objects. See step 2 for details about unused objects.

    If this checkbox is cleared, unused objects are included in the list of objects (their assignment to buffer pools is activated by the Assign objects not accessed during data collection checkbox on the previous page).

    Note: The state of the checkbox is retained for the next time you use the wizard.
  3. Click Next. If any rows contain errors, they are highlighted in red. You must correct these errors before you can continue to Step 4: Setting the initial buffer pool sizes and characteristics. You can click Back to return to the previous page.