Displaying general statistics for data sets processed by snapshot utilities
The top portion of the Snapshot data sets panel provides general performance statistics about data sets being processed by the snapshot component.
These statistics include data for all snapshot utilities data sets that fit the selection criteria that you have specified.
Snapshot Data Sets panel — General statistics for snapshot utilities
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Snapshot data sets on 02/25/2012 at 22:00:42
Allocated : 2457600 KB Used pct : 0 % Compress pct : 0 %
Data sets : 24 Hit pct : 1 % IHit pct : 0 %
Reads : 13065 ReadRate : 82 IReadRate : 0
Writes : 264 WriteRate : 1 IWriteRate : 0
CReads : 94 CReadRate : 0 CReadXfer : .003666
CWrites : 243 CWriteRate : 1 CWriteXfer : .000484
DReads : 12971 DReadRate : 81 DReadXfer : .002709
DWrites : 264 DWriteRate : 3 DWriteXfer : .053117
Select data sets and press Enter.
The following table describes the general information about the snapshot utility available on the top portion of the Snapshot data sets panel.
General statistics for data sets processed by snapshot utilities
Field | Description |
|---|---|
Allocated | The combined cache limit for the selected data sets The value of this field might be greater than the size of the extended buffer. This value is the amount available to hold preimages. |
Used pct | the percentage of the total cache limit for the selected data sets that is currently being used to cache preimages |
Compress pct | The compression ratio for the selected data set The compression percentage is calculated as the original number of bytes for a data set minus the number of bytes to cache the data set, divided by the original number of bytes, times 100. A high compression ration value indicates compression is working effectively. A negative compression rate indicates that expansion is occurring. Compression must be enabled for both the cache and the managed object for compression to be used. |
Data sets | The number of data sets that fit the selection criteria |
Hit pct | The percentage of read requests by the snapshot-enabled utility that were satisfied from the extended buffer for the selected data sets This value also indicates the percentage of pages for which preimage pages were retrieved from the extended buffer. |
IHit pct | The percentage of read requests by the snapshot-enabled utility that were satisfied from the extended buffer for the selected data sets during the most recently completed statistics interval These hits are preimages of data pages that were cached in the extended buffer. The actual data page has been updated since the snapshot utility job was registered. |
Reads | The total number of blocks read for the selected data sets by the snapshot-enabled utility (The reads might be from the extended buffer, from DASD, or from both.) |
ReadRate | The read access rate (in blocks per second) of the snapshot-enabled utility for the selected data sets since XBM was started (or since statistics were reset) |
IReadRate | The read access rate (in blocks per second) of the snapshot-enabled utility for the selected data sets during the most recently completed statistics interval |
Writes | The total number of blocks written to DASD by the DBMS for the selected data sets This statistic relates to updates that occur to the data sets while the XBM is processing the snapshot request. These writes cause preimages of data pages to be read into the extended buffer for snapshot processing. |
WriteRate | The write access rate (in blocks per second) by the DBMS for the selected data sets since XBM was started (or since statistics were reset) |
IWriteRate | The write access rate (in blocks per second) by the DBMS for the selected data sets during the most recently completed statistics interval |
CReads | The number of preimage data pages that were read by the snapshot-enabled utility from the extended buffer since the data sets were first activated |
CReadRate | The read access rate (in blocks per second) of the snapshot-enabled utility from the extended buffer while processing the snapshot |
CReadXfer | The time (in seconds per block) that the snapshot-enabled utility spent reading data from the extended buffer for the selected data sets while processing the snapshot Besides the actual extended buffer read time, the transfer time includes XBM processing time to bypass the DASD I/O request. |
CWrites | The total number of blocks written to the extended buffer for the selected data sets during snapshot processing |
CWriteRate | The write access rate (in blocks per second) to the extended buffer for the selected data sets |
CWriteXfer | The time (in seconds per block) spent writing data to the extended buffer for the selected data sets |
DReads | The total number of reads from DASD by the snapshot-enabled utility for the selected data sets during snapshot processing |
DReadRate | The disk read access rate (in blocks per second) by the snapshot-enabled utility for the selected data sets during snapshot processing |
DReadXfer | The time (in seconds per block) that the snapshot-enabled utility spent reading data from DASD for the selected data sets |
DWrites | The total number of blocks written to DASD by the DBMS for the selected data sets This statistic relates to updates that occur to the data sets while the XBM is processing the snapshot request. These writes cause preimages of data pages to be read into the extended buffer for snapshot processing. |
DWriteRate | The write access rate (in blocks per second) to DASD by the DBMS for the selected data sets |
DWriteXfer | The time (in seconds per block) that the DBMS spent writing data to DASD for the selected data sets |