Data Set Characteristics

The Data Set Characteristics report shows the characteristics of all data sets accessed for the measured job step during the measurement session.

The Data Set Characteristics report includes an entry for a data set if Strobe detected activity in the data set or computed a change in EXCP counts for it.

If the EXCP count changed but Strobe did not detect activity in the data set, the report shows only the DDNAME and the EXCP count, and other I/O reports in the Performance Profile have no entry for it.

Strobe records the characteristics from the Data Control Block (DCB) the Job File Control Block (JCFCB), or the Access Control Block (ACB) the first time it detects activity in that data set. It does not note whether subsequent activity has different characteristics.

Report details

• DDNAME is the data definition name assigned to the data set. For more information, see DDNAME.
• EXCP count shows, for VSAM data sets, the number of I/O operations performed on the data set during the measurement session. For more information, see EXCP.
• Access Method shows the access method used to process the data set. For more information, see Access-Method. 
• Record Size is the size of the maximum length record in bytes.
• Block/CI Size shows the block size of the data set, or VSAM control interval size, in bytes. If the data set is a concatenation of data sets, it gives the block size of the first data set in the concatenation. For files with high wait percentages in the Resource Demand Distribution report, the blocking factor may cause the inefficiency.
• Buffers represents different values depending on the specified access methods and buffering methods. For more information, see Buffers.
• LSR Pool is the LSR Pool number to which the data set is assigned. A value appears in this field only if LSR buffering is in effect. Click to view the VSAM LSR Pool Statistics report, which supplies additional information on pool activity.
• Hiper Buffers shows, for VSAM data sets, the number of hiperspace buffers assigned to the LSR subpool in which the file participates, not to the individual data set.
• CI Splits shows, for VSAM data sets, the number of control interval splits that occurred during the measurement session. A high number of CI splits suggests that you reorganize the file.
• CA Splits shows, for VSAM data sets, the number of control area splits that occurred during the measurement session. A high number of CA splits suggests that you reorganize the file.
• RPL (Request Parameter List) String Limit shows, for VSAM data sets, the number of request parameter lists that can be processed concurrently.
• The next line shows the fully qualified name of the data set associated with the data definition name (DDNAME). The data set name reported reflects the information available to Strobe when the file is first active. For a VSAM KSDS, the data set name may be a cluster name or a component name. For a VSAM alternate index, the data set name may be the component name, path name, or cluster name.

Click next to the DDNAME to view additional detail about the data set. You may need to click on a ribbon to reveal the detail within each ribbon:

• Record Information

  • Record Format defines the record and block format. For more information, see Record-format.

  • Extents shows the maximum number of extents allocated to the data set. Strobe reports on extents for concatenated data sets in this way: For concatenated sequential data sets, Strobe reports on extents for individual data sets in the concatenation. Strobe reports these extents only if it detects I/O activity for the data set. For concatenated partitioned data sets, Strobe reports extents for individual data sets in the concatenation.

  • Extended Format displays the presence of DFSMS Extended Format data sets and the attributes assigned to the data sets. For more information, see Extended-format.

  • Open Intent shows parameters the program supplied when it opened the data set. For more information, see Open-Intent.

  • Other Characteristics identifies various file characteristics, such as:

• File Statistics identifies response time statistics for data sets. For more information, see File-Statistics.
• VSAM shows information about VSAM data sets. For more information, see VSAM.
• SMS enables you to identify ways to reclassify a data set through System Managed Storage (SMS) to improve its performance. For more information, see System-Managed-Storage-Data.
• BatchPipes shows information about data sets processed by the BatchPipes subsystem. For more information, see BatchPipes.
• Alternate Information appears if the data set accessed is in the Hierarchical File System (HFS) or zFS File System. This section appears only if Strobe for UNIX System Services is installed at your site. For more information, see HFS-zFS-Data.