Chapter 9: Generating Image Copy Frequency Reports
This section contains the following topics:
Generate an Image Copy Frequency Report (see page 131) Image Copy Frequency Report Description (see page 132) How Extrapolated Changes are Calculated (see page 136)
Generate an Image Copy Frequency Report
The Image Copy Frequency report analyzes how often image copies are made in relation to the number of changes that are made to a tablespace. These changes include inserts, updates, and deletes. The report is a convenient method of determining whether local standards for disaster recovery are being met. The report also helps you determine whether the standards are still adequate for the level of database activity that is occurring. You can also see which tables are heavily updated between image copies. For example, you can specify a threshold of 1,000 to see which tables have had more than 1,000 updates between image copies.
Follow these steps:
1. Select 1 (Process Log) from the CA Log Analyzer Main Menu and press Enter.
The Report Specification panel appears.
2. Select Image Copy Frequency and press Enter.
The Image Copy Report Options panel appears.
3. Complete the following fields:
■ Specify a threshold in the Update Threshold field.
■ (Optional) use the Tablespace Filters field to include or exclude specific tablespaces from the report.
Press PF3 (End).
The Report Specification panel reappears.
4. Press PF3 (End) again.
The Report Source Specifications panel appears.
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5. Enter the range of data to analyze. Optionally, you can also specify a source of log data other than the BSDS or DB2 catalog. For example, you can specify a log extract file that you previously created. (See the next step.)
Press PF3 (End).
The Output Specifications panel appears.
6. Specify a destination for the extract file and report.
Note: The extract file contains the log data that is analyzed for the report. You can save the extract file to a data set and then reuse it for subsequent analysis. Saving the file lets you avoid rereading the log when generating further reports on the same data.
Press PF3 (End).
The Report Submission panel appears.
7. Specify an execution mode and press Enter.
The report is generated and saved to the specified destination.
Image Copy Frequency Report Description
An Image Copy Frequency report shows the tablespaces that exceeded a specified number of updates between image copies. Having too many updates between image copies can affect the recoverability of your tablespaces.
This report provides the following information, in the order shown:
■ The log extract summary, which identifies the log extract options and the Batch Processor statements that were used to generate the extract file. You specified a destination for the extract and its control file on the Process Log - Output
Specifications panel. These files are created whenever you use the BSDS or specific log data sets as the source of log data. You specified your batch execution
parameters on the Batch JCL Specification panel.
Chapter 9: Generating Image Copy Frequency Reports 133 This report section also provides the following information about the extract file:
PLA determined DB2 High log point
Identifies the highest log point that CA Log Analyzer has determined was written to the log when the extract file was generated.
PLR determined DB2 High log point
Identifies the highest log point the log reader has determined was written to the log when the extract file was generated.
High Processed DB2 log point
Identifies the log point of the highest UR that was encountered within the log processing range.
Note: This section appears only when you write the report to a data set or to SYSOUT. This section does not appear when the report is generated online for display at your terminal.
■ The log reporting options summary, which shows the Batch Processor statements that were used to generate the report.
Note: This section appears only when you write the report to a data set or to SYSOUT. This section does not appear when the report is generated online for display at your terminal.
■ The parmlib options, showing the highlevel.CDBAPARM(PLA) options that were in effect when you generated the report.
■ The image copy frequency section appears next, displaying the following information:
– The update threshold that you selected and the log range that was processed to generate the report. You specified the threshold on the Copy Report Options panel. You specified the log processing range on the Report Source
Specifications panel.
Note: This report description refers to the log processing range, the exception range, and the recovery range. The log processing range refers to the starting and ending log points that you specified on the Report Source Specifications panel. The exception range refers to portions of the log between image copies where the number of updates exceeds the specified threshold. This report focuses on the parts of the exception range that overlap the log processing range. The recovery range is similar to the exception range, but it refers to the portions of the log between image copies of tablespace partitions.
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– Each tablespace that exceeded the update threshold appears in this section.
The following information appears beneath each tablespace:
Max Changes to Recover
Identifies the maximum number of changes that would be recovered by a Point in Time recovery to any point within the exception range. These changes include inserts, updates, and deletes. This number can be an extrapolated number if the entire exception range does not fall within the specified log processing range.
Changes Encountered
Identifies the number of inserts, updates, and deletes in the portion of the exception range that falls within the specified log processing range.
Extrapolated Changes
Identifies the extrapolated value for inserts, updates, and deletes within the exception range. This value is based on the update activity and the amount of the exception range that falls within the specified log processing range. If the entire exception range falls within the log range, this number is the same as Changes Encountered.
Starting Image Copy
Identifies the last image copy that was taken before the tablespace exceeded the threshold value. The date and time and the start RBA of the image copy are shown. The date and time are taken from the TIMESTAMP column in SYSCOPY. The start RBA is taken from the START_RBA column in SYSCOPY. If no prior image copy is registered in SYSCOPY, START OF LOG is shown to represent the beginning of the log.
Ending Image Copy
Identifies the image copy that brings the tablespace below the threshold value. The date and time and the start RBA of the image copy are shown.
The date and time are taken from the TIMESTAMP column in SYSCOPY. The start RBA is taken from the START_RBA column in SYSCOPY. If no
subsequent image copy is registered in SYSCOPY, END OF LOG is shown to represent the end of the log.
Range Processed
Identifies the starting and ending log points for the portion of the
exception range that was processed. This section also shows the percent of the exception range that fell within the specified log processing range.
Chapter 9: Generating Image Copy Frequency Reports 135 If a tablespace is partitioned, the partition detail header appears beneath the preceding fields, with the following information:
Partition
Identifies the partition number.
Max Changes to Recover
Identifies the maximum number of changes that would be recovered by a Point in Time recovery to any point within the exception range. These changes include inserts, updates, and deletes.
Changes Encountered
Identifies the number of inserts, updates, and deletes to this partition in the portion of the exception range that falls within the log range.
Extrapolated Changes
Identifies the extrapolated value for inserts, updates, and deletes to this partition within the exception range. This value is based on the update activity and the amount of the exception range that falls within the specified log processing range. If the entire exception range falls within the log range, this number is the same as Changes Encountered.
If a tablespace is partitioned, the partition recovery ranges appear next. These ranges are the log ranges between image copies of this partition. The image copies can be either DSNUM ALL or DSNUM partno. All partition recovery ranges that overlap the exception range are listed here.
Recovery Range Start
Identifies the date and time and the start RBA of the first image copy for the partition. The date and time are taken from the TIMESTAMP column in SYSCOPY. The start RBA is taken from the START_RBA column in SYSCOPY.
If no prior image copy for this partition is registered in SYSCOPY, START OF LOG is shown to represent the beginning of the log.
Note: An asterisk preceding the value indicates that this log point is also the start of the exception range.
Recovery Range End
Identifies the date and time and the start RBA of the last image copy for the partition. The date and time are taken from the TIMESTAMP column in SYSCOPY. The start RBA is taken from the START_RBA column in SYSCOPY.
If no subsequent image copy for this partition is registered in SYSCOPY, END OF LOG is shown to represent the end of the log.
Note: An asterisk following the value indicates that this log point is also the end of the exception range.
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Number of Changes Encountered
Identifies the number of changes to this partition in the portion of the recovery range that falls within the specified log processing range. These changes include inserts, updates, and deletes. This value can differ from the number of changes within the exception range, which is given in the partition detail header.
Percent of Log Processed
Identifies the percentage of the recovery range that falls within the specified log processing range. This value is calculated to one one-hundredth of a percent.
Extrapolated Number of Changes
Identifies the extrapolated value for inserts, updates, and deletes to this partition within the recovery range. This value is based on the update activity and the amount of recovery range that falls within the specified log processing range. If the entire range falls within the log range, this number is the same as Number of Changes Encountered.
■ The index appears at the end of the report. If multiple reports are generated, the index appears after the last report. The index identifies each report that has been generated, the subheadings for each report, and their corresponding page numbers.
More information:
How Extrapolated Changes are Calculated (see page 136)
How Extrapolated Changes are Calculated
An Image Copy Frequency report refers to more than one type of range. The log processing range refers to the starting and ending log points that you specified on the Report Source Specifications panel. The exception range refers to portions of the log between image copies where the number of updates exceeds the specified threshold.
This report focuses on the parts of the exception range that overlap the log processing range. When the log range contains a portion of an exception range, CA Log Analyzer extrapolates the number of changes that occurred in the entire exception range.
The extrapolation takes into account the actual number of changes that were read. The extrapolation also considers the percent of the exception range that fell within the log processing range. CA Log Analyzer assumes that the frequency of changes is consistent with the actual changes that were read. For partitioned objects, the extrapolations are based on the log section between the beginning of the log range and the first tablespace image copy. The DSNUM value of the image copy does not matter.
Chapter 9: Generating Image Copy Frequency Reports 137 The following illustration shows a portion of the log. The RBA (Relative Byte Address) is shown in decimal. Actual RBAs are six-byte or 10-byte hexadecimal numbers. The extrapolated numbers appear in < >.
If an exception range exists between image copies #1 and #4, the percentage of the exception range that falls within the log range is calculated using the following formula:
log processing range (RBA 100 to 250) / exception range (RBA 50 to 300)=60.00%
Note: This percentage appears in the Image Copy Frequency report in the Range Processed fields.
The extrapolated changes for the log range from RBA 50 to 100 are calculated based on the number of updates between the start of the range and the next image copy. In partition 1, 10 changes occurred between the start of the log range (RBA 100) and the next image copy (image copy #2). To extrapolate the number of changes that occurred between image copies #1 and #2, CA Log Analyzer uses the following formula:
10 changes (for part 1) * entire range between copies (RBA 50 to RBA 150) / processed log range (RBA to RBA 150) = 20 changes.
The same formula is used for partition 2, even though image copy #2 is for partition 1, giving 200 changes. CA Log Analyzer extrapolates based on the update frequency closest to the range to limit the effect of changing table usage over time.
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To maintain consistency, the individual partition recovery ranges use the same extrapolated update counts as the entire exception range. However, Percent of Log Processed is calculated based on the range between copies for the individual partition.
For the partition 2 recovery range starting at copy #2 and ending at copy #4, the Number of Changes Encountered is 300. The Percent of Log Processed is the processed range (RBA 150 to RBA 250) divided by the whole range (RBA 150 to 300), yielding 66.67 percent. However, the Extrapolated Number of Changes is 500.
Note: The Extrapolated Number of Changes multiplied by the Percent of Log Processed does not equal the Number of Changes Encountered. As shown in the illustration, the number of changes to partition 1 appears to be increasing with time. As such, CA Log Analyzer extrapolates based on the update frequency closest to the unprocessed range.
More information:
Image Copy Frequency Report Description (see page 132)