Buffer Pool Statistics Detail
This panel provides detailed near-term history information about activity in a specified Db2 buffer pool during a selected report interval.
You can view information about a different buffer pool by entering a buffer pool ID (for example, 1 or 32K) next to HBPD.
________________ ZHBPD VTM O2 V550./C SE11 01/04/16 21:21:08 2
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===============================================================================
> BUFFER POOL STATISTICS DETAIL
HBPD 0
+ Collection Interval: 1 min Start: 07/31 21:20
+ Report Interval: 1 min Combine Level: NONE End: 07/31 21:21
+
+ Virtual Buffer Pool Size= 5000 VPOOL Frame Size = 4K
+ VPOOL Buffers Allocated = 5000 Minimum VPOOL Size = 0
+ VPOOL Buffers in Use = 29 Maximum VPOOL Size = 0
+
+ VPOOL Buffers to be Del = 0 Auto Size = N
+ Use Count = 65 Page Fix = N
+ VP Sequential Thresh = 80%
+ Deferred Write Thresh = 30% Vert Deferred Write Thresh = 5%
+ VP Parallel Seq Thresh = 50% Sysplex Parallel Thresh = 0%
+
+ Getpages per Sync I/O = .00 Pages Written per Write I/O = .00
+ Prefetch per I/O = .00 Pages Read per Prefetch = .00
+ Seq Prefetch per I/O = .00 Pages Read per Seq Prefetch = .00
+ List Prefetch per I/O = .00 Pages Read per List Prefetch= .00
+ Dyn Prefetch per I/O = .00 Pages Read per Dyn Prefetch = .00
+ Max Concur Prefetch = 0 Workfile Maximum = 0
+ BP Hit % - Random = .0% Virtual Page Steal Method = LRU
+ BP Hit % - Sequential = 99.9% Random Getpage Buffer Hit = 337
+ LWM Buffers on SLRU = 316 HWM Buffers on SLRU = 316
+
+ INTERVAL /MINUTE /THREAD /COMMIT
+ QUANTITY ( 1) ( 0) ( 0)
+ -------- ------- ------- -------
+ Getpage Requests 0 .00 .00 .00
+ Getpage Requests - Sequential 0 .00 .00 .00
+ Getpage Req - Seq Ovfl 0 .00 .00 .00 *DB2 12
+ Getpage Requests - Random 0 .00 .00 .00
+ Getpage Req - Random Ovfl 0 .00 .00 .00 *DB2 12
+ Getpage Failed - VPOOL Full 0 .00 .00 .00
+ Getpage Failed - Cond Request 0 .00 .00 .00
+ Getpage Failed - Cond SeqReq 0 .00 .00 .00
+
+ Sync Read I/O Operations 00 .00 .00 .00
+ Sync Read I/O - Sequential 0 .00 .00 .00
+ Sync Read I/O - Seq Ovfl 0 .00 .00 .00 *DB2 12
+ Sync Read I/O - Random 00 .00 .00 .00
+ Sync Read I/O - Random Ovfl 0 .00 .00 .00 *DB2 12
+ Pages Read via Seq Prefetch 0 .00 .00 .00
+ Seq Prefetch I/O Operations 0 .00 .00 .00
+ Sequential Prefetch Requests 0 .00 .00 .00
+ Pages Read via List Prefetch 0 .00 .00 .00
+ List Prefetch I/O Operations 0 .00 .00 .00
+ List Prefetch Requests 0 .00 .00 .00
+ Pages Read via Dyn Prefetch 0 .00 .00 .00
+ Dyn Prefetch I/O Operations 0 .00 .00 .00
+ Dyn Prefetch Requests 0 .00 .00 .00
+ Prefetch Failed - No Buffer 0 .00 .00 .00
+ Prefetch Failed - No Engine 0 .00 .00 .00
+
+ Parallel Group Requests 0 .00 .00 .00
+ Prefetch I/O Streams Reduced 0 .00 .00 .00
+ Parallelism Downgraded 0 .00 .00 .00
+ Prefetch Quan Reduced to 1/2 0 .00 .00 .00
+ Prefetch Quan Reduced to 1/4 0 .00 .00 .00
+ Pages Added to LPL 0 .00 .00 .00
+ Length of SLRU=VPSEQT 0 .00 .00 .00
+ Pages Updated 0 .00 .00 .00
+ Pages Written 0 .00 .00 .00
+ Page-in Required for Write I/O 0 .00 .00 .00
+ Write I/O Operations 0 .00 .00 .00
+ Immediate (Sync) Writes 0 .00 .00 .00
+
+ Vert Defer Wrt Thresh Reached 0 .00 .00 .00
+ Deferred Write Thresh Reached 0 .00 .00 .00
+ Data Manager Thresh Reached 0 .00 .00 .00
+
+ Successful VPOOL Expand/Contr 0 .00 .00 .00
+ VPOOL or HPOOL Expand Failed 0 .00 .00 .00
+
+ Successful Dataset Opens 0 .00 .00 .00
+ DFHSM Recall 0 .00 .00 .00
+ DFHSM Recall Timeouts 0 .00 .00 .00
+
+ Sort Merge Passes 0 .00 .00 .00
+ Sort/Merge Workfile Requests 0 .00 .00 .00
+ Sort/Merge Workfile Req Denied 0 .00 .00 .00
+ Sort Merge Pass - Buff Short 0 .00 .00 .00
+ Workfile Prefetch Disabled 0 .00 .00 .00
+ Workfile Create Failed-No Buff 0 .00 .00 .00
+ Destructive Read Requests 0 .00 .00 .00
+ Destructive Read Page Dequeue 0 .00 .00 .00
===============================================================================Highlighting
OMEGAMON for Db2
PE highlights some fields in this panel to
draw your attention to their current status:
| Field | Exception | Reason |
|---|---|---|
|
Number of Pages in Use |
BXPN | The pages in use exceeded the minimum defined. |
| BMAX | The pages in use reached the maximum defined. | |
| BMTH | The percentage of pages in use has reached the predetermined threshold. |
Navigation
For additional information about:
- Related topics, select one of the options at the top of the panel.
- Other topics, use the PF keys.
Fields
- Collection Interval
- The time interval specified for the collection of near-term history data. This unit of time was specified when the Near-Term History Data Collector was started.
- Start
- The start time of the interval currently displayed.
- Report Interval
- This field determines the report interval. It is set on the Near-Term History Report Option panel.
- Combine Level
- This field reflects the selected combine level. If Combine Level is NONE, the
report interval is the same as the collection interval. Possible values:
- HOURLY
- Data will be reported in hourly intervals.
- NONE
- Data will be reported in the time unit specified by the collection interval.
- End
- The end time of the interval currently displayed.
- Virtual Buffer Pool Size
- The number of buffers allocated for an active virtual buffer pool.
- VPOOL Frame Size (QDBPFRAM)
- For the Frame Size attribute, you can specify the values
4K,1M, or2G.This applies to Db2 11 and higher.
- VPOOL Buffers Allocated
- The number of virtual buffer pool pages that were allocated at the end of the interval.
- Minimum VPOOL Size (QDBPVPMI)
- The VPSIZEMIN attribute.
This applies to Db2 11 and higher.
- VPOOL Buffers in Use
- The number of virtual buffer pool pages that were in use (nonstealable) at the end of the interval.
- Maximum VPOOL Size (QDBPVPMA)
- The VPSIZEMAX attribute.
This applies to Db2 11 and higher.
- VPOOL Buffers to be Del
- The number of pages to be deleted from an active virtual buffer pool as a result of pool contraction.
- Auto Size
- Determines whether Auto Size is used. You can specify
Y(YES) orN(NO). - Use Count
- The number of open tablespaces or indexspaces in this buffer pool.
- Page Fix
- Determines whether a page is fixed in real storage when it is first used. You can specify
Y(YES) orN(NO). - VP Sequential Thresh
- Sequential Steal threshold for the virtual buffer pool VPSSEQT. The percentage of the virtual buffer pool that might be occupied by sequentially accessed pages. If set to zero, prefetch is disabled.
- Vert Deferred Write Thresh
- Vertical Deferred Write threshold for the virtual buffer pool VDWQT. The percentage of the buffer pool that might be occupied by updated pages from a single data set.
- VP Parallel Seq Thresh
- Parallel I/O sequential threshold VPPSEQT. This threshold determines how much of the virtual buffer pool might be used for parallel I/O operations. It is expressed as a percentage of VPSEQT. If set to zero, I/O parallelism is disabled.
- Sysplex Parallel Thresh
- Virtual buffer pool assisting parallel sequential threshold. This threshold determines how much of the virtual buffer pool might support parallel I/O operations from another Db2 in a data sharing group.
- Getpages per Sync I/O
- The ratio of Getpage requests to Read I/Os.
- Pages Written per Write I/O
- The ratio of page writes to physical I/Os.
- Prefetch per I/O
- The ratio of Prefetch requests to physical I/Os.
- Pages Read per Prefetch
- The ratio of pages read by Prefetch processing to total Prefetch requests. This includes both Sequential Prefetch and List Prefetch.
- Seq Prefetch per I/O
- The ratio of pages read by Sequential Prefetch to Sequential Prefetch I/O.
- Pages Read per Seq Prefetch
- The ratio of pages read by Sequential Prefetch requests to Sequential Prefetch requests.
- List Prefetch per I/O
- The ratio of List Prefetch requests to List Prefetch I/Os.
- Pages Read per List Prefetch
- The ratio of pages read by List Prefetch to List Prefetch requests.
- Dyn Prefetch per I/O
- The ratio of Dynamic Prefetch request to Dynamic Prefetch I/Os.
- Pages Read per Dyn Prefetch
- The ratio of pages read by Dynamic Prefetch to Dynamic Prefetch request.
- Max Concur Prefetch I/O
- The highest number of concurrent prefetch I/O streams that were allocated to support I/O parallelism.
- Workfile Maximum
- The maximum number of workfiles that have been allocated during sort/merge processing.
- BP Hit % - Random
- The percentage of times that Db2 performed a Getpage operation with a random request and the page was already in the buffer pool. A DASD read was not required.
- Virtual Page Steal Method
- Determines when and whether performance-critical objects in buffer pools are removed from buffer
pools when the space is needed by other objects. Valid values:
- LRU
Least Recently Used
objects are removed first.- FIFO
- Oldest objects are removed first (First-In-First-Out).
- NONE
- Objects are not removed from buffer pool (no page stealing). This setting provides the highest availability for business-critical objects.
- BP Hit % - Sequential
- The percentage of times that Db2 performed a Getpage operation with a sequential request and the page was already in the buffer pool. A DASD read was not required.
- Random Getpage Buffer Hit
- The number of times that the random Getpage request has a buffer hit and the buffer is on the least-recently-used (SLRU) chain. Db2 11 and later. (Field name: QBSTRHS)
- LWM Buffers on SLRU
- The minimum number of buffers on the sequential least-recently-used (SLRU) chain in the last statistical period. This is the low-water mark (LWM) within an interval. Db2 11 and later. (Field name: QBSTSMIN)
- HWM Buffers on SLRU
- The maximum number of buffers on the sequential least-recently-used (SLRU) chain in the last statistical period,. This is the low water mark (LWM) within an interval. Db2 11 and later. (Field name: QBSTSMAX)
For each of the following fields, the following statistics are provided:
- INTERVAL QUANTITY
- The amount of activities that occur during the interval.
- /MINUTE
- Rate per minute. The number under /MINUTE (in parentheses) is the number of minutes in the interval.
- /THREAD
- Rate per thread. The number under /THREAD (in parentheses) is the number of Create Threads during the interval.
- /COMMIT
- Rate per Commit. The number under /COMMIT (in parentheses) is the number of Commit requests (including abort requests) during the interval.
- Getpage Requests
- Getpage request operations for the buffer pool during the interval.
- Getpage Requests - Sequential
- Number of Getpage requests issued by sequential access requestors.
- Getpage Requests - Random
- Number of Getpage requests issued by random access requestors.
- Getpage Requests - Seq Ovfl
- The number of sequential GETPAGE requests using overflowed buffers. Db2 12 and later.
- Getpage Requests - Random Ovfl
- The number of non-sequential GETPAGE requests using overflowed buffers. Db2 12 and later.
- Getpage Failed - VPOOL Full
- Number of Getpage failures due to unavailable buffers because the virtual buffer pool was full.
- Getpage Failed - Cond Request
- Number of conditional Getpage requests that could not be satisfied for this buffer pool. A conditional Getpage is used with parallel I/O processing only.
- Getpage Failed - Cond SeqReq
- The number of conditional sequential getpage requests that failed because the page is not in the buffer pool.
- Sync Read I/O Operations
- Synchronous read operations done by Db2 during the interval.
- Sync Read I/Os - Sequential
- Number of synchronous Read I/O operations performed by sequential requests.
- Sync Read I/Os - Random
- Number of synchronous Read I/O operations performed by random requests.
- Sync Read I/Os - Seq Ovfl
- The number of synchronous Read I/O operations performed for sequential GETPAGE requests using overflowed buffers. Db2 12 and above. (QBSTASSE)
- Sync Read I/Os - Random Ovfl
- The number of synchronous Read I/O operations performed for non-sequential GETPAGE requests using overflowed buffers. DB12 and above. (QBSTASYN)
- Page-in Required for Read I/O
- Number of page-ins required for Read I/O.
- Pages Read via Seq Prefetch
- Pages read as a result of Sequential Prefetch requests.
- Seq Prefetch I/O Operations
- Number of asynchronous Read I/Os caused by Sequential Prefetch.
- Sequential Prefetch Requests
- Sequential Prefetch requests for the buffer pool during the interval.
- Pages Read via List Prefetch
- Number of pages read because of List Prefetch.
- List Prefetch I/O Operations
- Number of asynchronous Read I/Os caused by List Prefetch.
- List Prefetch Requests
- List Prefetch requests for the buffer pool during the interval.
- Pages Read via Dyn Prefetch
- Number of pages read because of Dynamic Prefetch. Dynamic prefetch is triggered because of sequential detection.
- Dyn Prefetch I/O Operations
- Number of asynchronous Read I/Os caused by Dynamic Prefetch.
- Dyn Prefetch Requests
- Dynamic Prefetch requests for the buffer pool.
- Prefetch Failed - No Buffer
- Failures of Sequential Prefetch because the Sequential Prefetch threshold (SPTH) was reached.
- Prefetch Failed - No Engine
- Failures of Sequential Prefetch because the maximum number of concurrent Sequential Prefetches was reached. (You cannot change this maximum value.)
- Parallel Group Requests
- Number of requests made for processing queries in parallel.
- Prefetch I/O Streams Reduced
- Number of requested prefetch I/O streams that were denied because of a buffer pool shortage. This applies only for nonworkfile pagesets for queries that are processed in parallel.
- I/O Parallelism Downgraded
- Number of times the requested number of buffers to allow a parallel group to run to the planned degree could not be allocated because of a buffer pool shortage.
- Prefetch Quan Reduced to 1/2
- Number of times the Sequential Prefetch quantity was reduced from normal to one-half of normal. This is done to continue to allow execution concurrently with parallel I/O.
- Prefetch Quan Reduced to 1/4
- Number of times the Sequential Prefetch quantity was reduced from one-half to one-quarter normal.
- Pages Added to LPL
- The number of times one or more pages are added to logical page lists (LPL). (Field name: QBSTLPL)
- Length of SLRU=VPSEQT
- The number of times when the length of the sequential least-recently-used (SLRU) chain equals the sequential steal threshold VPSEQT. DB11 and later. (Field name: QBSTHST)
- Pages Updated
- Updates to pages in the buffer pool during the interval.
- Pages Written
- Buffer pool pages written to DASD during the interval.
- Page-in Required for Write I/O
- Number of page-ins required for Write I/O operations.
- Write I/O Operations
- Writes performed by media manager for both synchronous and asynchronous I/O.
- Immediate (Sync) Writes
- immediate Writes to DASD during the interval. This
value is incremented when 97.5% of the buffer pool pages are in use.
In addition, Db2 might flag
buffer pool pages for immediate Write during checkpoint processing
and when a database is stopped. Note: Consider the value of DMTH (Data Manager threshold) when interpreting this value. If DMTH is zero, this value is probably insignificant.
- Write Engine Not Available
- Writes that were deferred because Db2 reached its maximum number of concurrent Writes.
- Vert Defer Wrt Thresh Reached
- The number of times the Vertical Deferred Write threshold was reached.
- Deferred Write Thresh Reached
- Deferred Write threshold (DWTH) was reached. This occurs when Db2 uses 50% of the buffer pool minimum value, or if a data set has updated 10% of the pages or 64 pages, whichever is greater. At this threshold, Db2 forces writes in an effort to free pool space.
- Data Manager Thresh Reached
- Data Manager threshold (DMTH) was reached. This occurs when Db2 uses 95% of the buffer pool minimum value and begins to operate at the row level rather than the page level. When this occurs, CPU usage rises significantly.
- Successful VPOOL Expand/Contr
- Number of successful virtual buffer pool expansions or contractions because of the ALTER BUFFERPOOL command.
- VPOOL Expand Failed
- Number of virtual buffer pool expansion failures.
- Successful Dataset Opens
- The number of successful data set Open operations during the interval.
- DFHSM Recall
- Attempts to access data sets that were migrated by DFHSM.
- DFHSM Recall Timeouts
- Unsuccessful attempts to recall data sets because the timeout threshold (DSNZPARM RECALLD) was exceeded.
- Sort/Merge Passes
- Number of merge passes for Db2 sort/merge processing.
- Sort/Merge Workfile Requests
- Number of workfiles requested during sort/merge processing.
- Sort/Merge Workfile Req Denied
- Number of requests for workfiles denied during sort/merge processing due to insufficient buffer resources.
- Sort/Merge Pass - Buff Short
- Number of times that sort/merge could not efficiently perform due to insufficient buffer resources. This field is incremented when the number of workfiles allowed is less than the number of workfiles requested.
- Workfile Prefetch Disabled
- Number of times workfile prefetch was not scheduled because the prefetch quantity was zero.
- Workfile Create Failed-No Buff
- Number of times a workfile was not created due to insufficient buffers (MVS/XA) only.
- Destructive Read Requests
- Number of pages requested for destructive read processing.
- Destructive Read Page Dequeue
- Number of pages dequeued for destructive read processing.