Alter Buffer Pool Command Issued
This topic shows detailed information about "System Parameters - Alter Buffer Pool Command Issued".
System Parameters - Alter Buffer Pool Command Issued
The field labels shown in the following sample layout of "System Parameters - Alter Buffer Pool Command Issued" are described in the following section.
ALTER BUFFER POOL COMMAND ISSUED OLD NEW
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TIMESTAMP 11/12/14 15:03:23.56 VPOOL SIZE (PAGES) 0 10
BUFFER POOL ID BP25 VPOOL SEQ THRESH 80 80
HORIZ DEFER WRITE THRESH 30 30
VERT DEFER WRITE THRESH (%) 5 5
VERT DEFER WRITE THRESH (BUF) 0 0
VPOOL PARALLEL SEQ THRESH 50 50
ASSISTING PARALLEL SEQ THRESH 0 0
PGFIX ATTRIBUTE NO NO
PAGE STEAL METHOD LRU LRU
AUTOSIZE NO NO
FRAMESIZE 4K 4K
VPOOL SIZE MIN 0 0
VPOOL SIZE MAX 0 0
SIM POOL SIZE 200 300
SIM POOL SEQ THRESH 50 75 - BUFFER POOL ID
The buffer pool internal identifier. The values 0 through 49 are the identifiers for BP0 through BP49. The values 80 through 89 are the identifiers for BP32K through BP32K9.
Field Name: QW0201BP
- VPOOL SIZE (PAGES) (OLD)
The size of the old virtual pool.
Field Name: QW0201OP
- VPOOL SIZE (PAGES) (NEW)
The size of the new virtual buffer pool.
Field Name: QW0201NP
- VPOOL SEQ THRESH
The old and new virtual pool sequential steal threshold.
Old status taken from the DB2 field QW0201OT.
New status taken from the DB2 field QW0201NT.
Field Name: RT0201VS
- HORIZ DEFER WRITE THRESH
This threshold is a percentage of the virtual buffer pool that might be occupied by unavailable pages, including updated pages and pages in use.
The default value for QWQT is 30%. You can change this value to
any value from 0% to 90% using the DWQT option of the ALTER
BUFFERPOOL command.
DB2 checks QWQT when an update to a page is complete. If the percentage of unavailable pages in the virtual buffer pool exceeds QWQT, write operations are scheduled for up to 128 pages per data set to decrease the number of unavailable buffers to 10% below QWQT. For example, if QWQT is 50%, the number of unavailable buffers is reduced to 40%.
When the limit of QWQT is reached, data sets containing the oldest updated pages are written asynchronously. DB2 continues to write pages until the ratio goes below the QWQT.
Field Name: QDBPDWQT
- VERT DEFER WRITE THRESH (%)
The vertical deferred write threshold for the virtual buffer pool expressed as percentage.
Old status taken from the DB2 field QW0201OV.
New status taken from the DB2 field QW0201NV.
Field Name: RT0201PC
- VERT DEFER WRITE THRESH (BUF)
The vertical deferred write threshold for the virtual buffer pool expressed as an absolute number of buffers. It is only used if VERTICAL DEFERRED WRITE THRESHOLD (PERCENTAGE) is 0.
Old status taken from the DB2 field QW0201OJ.
New status taken from the DB2 field QW0201NJ.
Field Name: RT0201BU
- VPOOL PARALLEL SEQ THRESH
The old and new virtual pool parallel sequential threshold.
Old status taken from the DB2 field QW0201OQ.
New status taken from the DB2 field QW0201NQ.
Field Name: RT0201VP
- ASSISTING PARALLEL SEQ THRESH
The assisting parallel sequential threshold before and after the ALTER BUFFERPOOL command was issued.
Old status taken from the DB2 field QW0201OX.
New status taken from the DB2 field QW0201NX.
Field Name: RT0201AS
- PGFIX ATTRIBUTE
Indicates whether a page is fixed in real storage when it is first used. It can have one of the following values: YES or NO.
Field Name: QDBPPFIX
- PAGE STEAL METHOD
- Identifies the page stealing algorithm (PGSTEAL) that is used for the virtual buffer pool. It controls when and whether performance-critical objects in buffer pools are removed from buffer pools when the space is needed by other objects. Possible values are:
- LRU
- Least recently used (LRU) objects are removed first. This means it takes away pages that are not used so that more recently used pages can remain in the virtual buffer pool. This is used by default.
- FIFO
- First-In-First-Out (FIFO) means that the oldest objects are removed first. This results in a small decrease in the cost of a Getpage operation. It can reduce internal DB2 latch contention in environments that require very high concurrency.
- NONE
- Objects are not removed from buffer pool (no page stealing). This setting provides the highest availability for business-critical objects.
Old status taken from the DB2 field QW0201OK.
New status taken from the DB2 field QW0201NK.
Field Name: RT0201PS
- AUTOSIZE
The old and new status of the AUTOSIZE attribute.
Old status taken from the DB2 field QW0201OZ.
New status taken from the DB2 field QW0201NZ.
Field Name: RT0201AT
- FRAMESIZE (OLD)
The size of the old frame (4 KB,1 MB, or 2 GB).
Field Name: QW0201OC
- FRAMESIZE (NEW)
The new frame size (4 KB, 1MB, or 2GB).
Field Name: QW0201NC
- VPOOL SIZE MIN (OLD)
The minimum size of the old virtual pool.
Field Name: QW0201OA
- VPOOL SIZE MIN (NEW)
The minimum size of the new virtual pool.
Field Name: QW0201NA
- VPOOL SIZE MAX (OLD)
The maximum size of the old virtual pool.
Field Name: QW0201OB
- VPOOL SIZE MAX (NEW)
The maximum size of the new virtual pool.
Field Name: QW0201NB
- SIM POOL SIZE
The number of simulated buffers specified for the simulated buffer pool. Old value is taken from the DB2 field QW0201OS. New value is taken from the DB2 field QW0201NS.
Field Name: RT0201SZ
- SIM POOL SEQ THRESH
The sequential steal threshold for the simulated buffer pool, expressed as a percentage of the total simulated buffer pool size. Old value is taken from the DB2 field QW0201OH. New value is taken from the DB2 field QW0201NH.
Field Name: RT0201ST