Step 4: Setting the initial buffer pool sizes and characteristics
About this task
When you have performed Step 3: Assigning objects to buffer pools,
the fourth page of the object placement wizard is displayed: Figure 1. Object Placement – The Buffer Pool Size and Characteristics
window
This page shows the recommended initial buffer pool
sizes and thresholds for the individual buffer pools, and shows the
total storage required for these recommendations.
The value in the Planned field, shown at
the top of the page, is the sum of the Total virtual pool
size and the Total hiper pool size.
These are the pool sizes (in MB) that you have specified in Step 1: Selecting a pattern file.
The object placement and sizing algorithm has used
this total storage to calculate the initial virtual sizes for the
individual buffer pools, based on the object placements specified
in the User-defined column on the previous page.
The sum of all buffer pool sizes (the recommended number of pages
for a buffer pool, multiplied by the page size of the buffer pool
in MB) yields the planned size in MB.
By default, the sizing algorithm allocates a minimum buffer pool
size of 20% of the average buffer pool size for buffer pools to which
objects are assigned.
You can use this page to adjust the initial buffer pool
sizes and thresholds of individual buffer pools. Buffer Pool Analyzer
will use the adjusted values when it generates the DB2® ALTER
BUFFERPOOL commands and SQL ALTER statements.
If you change the virtual buffer pool size of one of the listed
buffer pools, the New size, at the top of the page,
reflects the new sum (in MB). Initially, Planned and New show
the same value. (Small differences are possible because only integer
pages are calculated, not fractions.)
To change a value, double-click the value and edit it. Then, press
Enter or select a different field.
Note that the size of buffer pools that no longer have
objects assigned to them is set to zero. When you apply the recommendations
from the object placement and buffer pool sizing, access to objects
assigned to these buffer pools is disabled.
The following list
describes the elements of the buffer pool sizings, as shown on the
page. Note that you can edit these values, except the buffer pool
names. For more detailed information, see also The Buffer Pool Characteristics section. Note that
you can sort the list by clicking a column header of choice one or
more times. Small arrows indicate the sort order. By default, the
list is sorted by Name.
Name
Shows the name of the buffer pool.
VP Size [pages]
Shows the recommended virtual buffer pool size, in number of pages,
for the affected buffer pool.
VP Seq [%]
Shows the recommended virtual pool sequential steal threshold
(VPSEQT) for the affected buffer pool. This is the portion of the
buffer pool that can be occupied by sequentially accessed pages. For
more details, see Thresholds
— Virtual sequential in The Buffer Pool Characteristics section.
DefWrite [%]
Shows the recommended deferred write threshold (DWQT) for the
affected buffer pool. This is the percentage of the buffer pool that
can be occupied by unavailable pages. For more details, see Thresholds
— Deferred write in The Buffer Pool Characteristics section.
VertDefWrite [%]
Shows the recommended vertical deferred write threshold (VDWQT)
for the affected buffer pool. This is the percentage of the buffer
pool that can be occupied by updated pages of a single page set. For
more details, see Thresholds
— Vert deferred write in The Buffer Pool Characteristics section.
Review the recommended initial buffer pool sizes and thresholds.
Adjust them, if required.
Click Finish, or Back to
return to the previous page.
When the object placement wizard finishes,
the result is immediately shown in a new browser window. In addition,
the result is saved in the Results subfolder
of the Object Placement folder for later viewing.
