Step 2: Assigning objects to buffer pools

About this task

When you have opened a trace data file, as described in Selecting and opening a trace data file, and have clicked the Object to Buffer Pool Assignment tab, the following page is displayed:
Figure 1. Simulation – The Object Assignment window
This figure is a graphical representation of the Object Assignment window from a simulation.
This page shows objects and their assignments to buffer pools for this simulation, and provides controls to change these assignments.
  • The list on the left side shows selectable objects, their original placements (in column Trace buffer pool), and their assignments (in column Simulation buffer pool) for this simulation.

    The objects are shown in different sub-pages according to their sizes. Click the 4K, 8K, 16K, or 32K tab to see the respective objects. Note that these selections also change several button labels dynamically.

    The Name field shows the name of the object. The Type field identifies the object as a table space (TS) or index space (IX). DB ID shows the corresponding database ID. OB ID shows the object ID.

    The Trace buffer pool field shows the name of the buffer pool where the object is originally placed (determined from the content of the trace data file). The Simulation buffer pool field shows the name of the buffer pool to which the object is assigned for this simulation. Initially, before you change an assignment, both names are identical.

  • On the right side the previously selected buffer pools are shown, and controls are given to change the objects' assignments for this simulation. Further, status information about the assignments is shown.

    The Current simulation buffer pools field lists the names of the buffer pools to be simulated (those selected during the previous step). If the list becomes too long, which is indicated by trailing dots (…), move the mouse pointer above the list to display the complete list.

    The Total number of objects field shows the total number of active objects contained in the trace data file. Active objects are objects for which buffer pool activities were recorded during the time trace data was collected (unlike inactive objects and objects in the DB2® catalog).

    The Number of objects for simulation field shows the number of objects that are assigned to the current simulation buffer pools.

You use this page to change the assignment of objects to buffer pools for this simulation.
  • Initially, the assignments are not changed. The buffer pool names in columns Trace buffer pool and Simulation buffer pool are identical for each object. If the assignments are not changed, the simulation is performed with the assignments that were active at the time trace data was collected.
  • Objects can be assigned to buffer pools of matching page sizes (4 KB objects to 4 KB buffer pools, and so on). Use the 4K, 8K, 16K, or 32K tab to see and assign the respective objects.
  • You can assign objects to any matching buffer pool, independently of whether a buffer pool is selected for this simulation. However, the simulation considers only those objects that are assigned to the buffer pools currently selected for simulation. Your assignments are saved and can be used for other simulations that use the same trace data file. The assignments are used if you select the corresponding buffer pools for simulation on the Simulation Parameters page.

    To view only objects in the list that are assigned to the buffer pools to be simulated, select the Show only 4K objects for current simulation buffer pools check box. (The objects' page size changes dynamically.) If this check box is cleared, all objects (of that page size) that are contained in the trace data file are shown.

  • To select a single object for an assignment, click the name of an object. 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 assign one or more selected objects to a buffer pool, select a buffer pool from the Buffer pool list and click Set.
  • To return one or more selected objects to their original placements, click Reset. To return all objects of the currently displayed page size, for example, 4 KB objects, click Reset 4K (the button label changes dynamically). To return all objects, independently of their page sizes, click Reset All.
  • Note that you can sort the list by clicking a column header of choice one or more times. Small arrows indicate the sort order.

  1. Review your assignments and adjust them as required.
  2. If you have already performed Step 1: Setting simulation parameters, click OK to start the simulation. Otherwise complete Step 1: Setting simulation parameters before you start the simulation.

    When the simulation starts, a progress indicator is shown. Note the estimated completion time. If you want to stop the simulation before completion, click Cancel. Control is returned to the Db2 Buffer Pool Analyzer - Simulation window.

    When the simulation finishes, the result is saved in the Results subfolder of the Simulation folder for later viewing. You are asked whether the simulation report should be opened now.
    • Yes immediately displays the result in a new browser window. The Db2 Buffer Pool Analyzer - Simulation window is closed.
    • Cancel returns control to the Db2 Buffer Pool Analyzer - Simulation window.
  3. Continue with Viewing the result of a simulation cycle.