Configuring a collect task

This section explains how to specify details of a collect task, such as the type of data to collect, and the start and stop conditions.

 06/23/13 14:16    Collect Report Data for Buffer Pool Analysis

                               Trace Configuration

   Command ===> ______________________________________________________________

   Task description . . . . : Collect data for buffer pool activity

   Output DS name . . . . . : 'NKA.COLLECT.TRACE'
   Disposition  . . . . . . : 3  1=Append
                                 2=Overwrite
                                 3=New

   Record format  . . . . . : 1  1=Standard
                                 2=Short

   Data type  . . . . . . . : 2  1=Detail
                                 2=Summary
                                 3=Catalog only

   OP buffer size . . . . . : 512   kB

   Start the DB2 trace  . . : 1  1=Immediately
                                 2=At 15 : 14 : 0  (hh:mm:ss)

   Trace and collect data . : 1  1=Continuously
                                 2=Every 5    minutes for 60   seconds

   Stop the DB2 traces when any of the following conditions occur:
   (Select at least one condition.)
   >  Elapsed time  . . . . . . . : 0       seconds
   >  Number of records collected : 0

    F1=Help     F2=Split    F3=Exit     F7=Up       F8=Down     F9=Swap
   F12=Cancel

1. In the field Output DS name specify the data set name to which the data is to be written.
   Data sets used for this purpose should have a variable record format (RECFM) and a record length (LRECL) of at least 6000. The data set name should have the low-level qualifier TRACE, for example NKA.COLLECT.TRACE, for the following reasons:

   • If this data set contains trace data that will be used for simulations on the client, the downloaded file on the client must have a file name extension of trace. Keeping the extension on both sides also eases the download procedure.
   • Avoid BPD as low-level qualifier because this qualifier is recommended for bpd files that are created from trace data. The reason is that bpd files must have a file name extension of bpd on the client.
2. In the field Disposition specify how the data is to be written to the specified data set:

   1=Append

   Data collected during this task is appended to any previously collected data in the named data set.

   The disadvantage of appending data to existing data is that a copy of the catalog data is appended every time. If you want to use the data on the client, the bpd file becomes unnecessarily large and difficult to handle. Furthermore, if the system setup changes between two collect tasks, some report values can become undefined. If possible, use one of the following options.

   If you collect data for a simulation on the client, never use this option.

   2=Overwrite

   Data collected during this task overwrites any previously collected data in the named data set.

   3=New

   The data set is allocated dynamically with RECFM=VBS, LRECL=32756, and BLKSIZE=6233 before data is written to it.

3. In the field Record format specify which IFCID record header information you want to be included in the collected data:

   1=Standard

   Includes the complete IFCID record header.

   Select this option if you want to create comprehensive activity reports. Standard provides the information that is used by the INCLUDE, EXCLUDE, ORDER, and SORT options of the BPACTIVITY REPORT command.

   Do not use this option if you want to use the data for simulation.

   2=Short

   Includes only part of the IFCID record header.

   Select this option if you want to use the data for the client-based functions. This option is mandatory for simulation.

   For most activity reports Short is also sufficient.

4. In the field Data type specify which DB2® trace data you want to collect:

   1=Detail

   Collects buffer pool statistics, catalog data, and buffer pool activity data.

   Select this option if you want to create detail activity reports, or bpd files or trace data files for use on the client. This option is mandatory for simulation.

   2=Summary

   Collects buffer pool statistics and catalog data.

   Select this option if you want to create summary activity reports.

   Note: Db2 updates summary data at statistics intervals. When you specify the duration of the collect task, permit for sufficient time to capture several intervals. If required, seeDetermining when and how long to collect and Preliminary remarks about the accuracy of summary and detail reports for more details.

   3=Catalog only

   Collects only catalog data. For possible uses see Concatenating trace data for activity reports and bpd files

5. In the field OP Buffer size specify a value from 8 KB to 1024 KB. The Online Performance (OP) buffer is used by Db2 to pass the trace data to Buffer Pool Analyzer (and other monitor programs).

   Specify a large buffer size to prevent a buffer overflow.

   Specify a moderate buffer size if you are constrained on virtual storage in DB2's database services address space (DBM1).

6. In the field Start the DB2 trace specify one of the following start conditions:

   1=Immediately

   Starts the Db2 trace immediately.

   2=At (hh:mm:ss)

   Starts the Db2 trace at a specified time, whereby hh is the hour, mm is the minute, and ss is the second. If the specified time is less than the current time, the trace starts the next day at the specified time. Note that a trace is stopped if you leave Db2 Performance Expert or Buffer Pool Analyzer. See also step 4.

7. In the field Trace and collect data specify how the data is to be traced:

   1=Continuously

   Runs the Db2 trace for the entire tracing period. Select this option if you want to use the trace data for simulation.

   2=Every x minutes for y seconds

   Runs the Db2 trace every x minutes for y seconds, whereby x denotes the specified minutes, and y denotes the specified seconds.

8. Specify one or two stop conditions for the Db2 trace. The trace stops when one of the conditions becomes true.
   • Activate one or both stop conditions by typing a slash (/) in the field preceding the condition. A greater-than (>) symbol in this field indicates that this condition was previously selected.
   • Specify one or both conditions as follows:
     • In the field Elapsed time specify the number of seconds the trace should run.
     • In the field Number of records collected specify a maximum number of records to be collected.
       Examples:

       • 10000
       • 100K (for 100000)
       • 1M (for 1000000)

         If you want to use the trace data for simulation, ensure that you collect trace data for approximately 20 minutes, respectively 1200 seconds. In the field Elapsed time specify an appropriate value. Either deactivate the Number of records collected condition, or set it to 13000000 (approximately 2 GB of data), to ensure that the trace does not stop earlier.