Relationship of the dictionary record to the performance records: field connectors

Following the SMF product section that relates to the performance records, and before the performance records themselves, is a string of field connectors. The field connectors connect each performance record field to the dictionary entry that describes it.

The purpose of the field connectors is to tell you which fields are going to occur in the performance records produced by this CICS® run. Each field connector corresponds to one field in each of the succeeding performance records. The first field connector corresponds to the first field, the second to the second field, and so on.

Each field connector also corresponds to a single dictionary entry in the associated dictionary record: the connector value is equal to the value of CMODCONN in the corresponding dictionary entry. A useful technique for calculating the offset of a particular dictionary entry is to take the connector, subtract one, and multiply the result by the length of a single dictionary entry.

Thus, the string of field connectors is the key to the dictionary. And without the dictionary, reporting and analysis programs cannot interpret the performance data.

The successive performance records can be regarded as rows in a table, with each column corresponding to one type of field within the records. Each field connector then describes the contents of one column. This view of the data is helpful when designing tabular reports, which are often arranged in this way.

Figure 1 illustrates the relationship between the dictionary record, the field connectors, and the performance records.

The picture shows a dictionary record consisting of dictionary entries numbered 1 to n. Below the dictionary record is a string of field connectors, also numbered 1 to n. Below this are several performance records, each consisting of data fields numbered 1 to n. Field connector 1 connects dictionary entry 1 to data field 1 in the performance records. Field connector 2 connects dictionary entry 2 to data field 2 in the performance records, and so on. The data that is defined by dictionary entry 3 has been excluded, so there is no field connector value for it and it does not appear in the performance records. — Figure 1. Relationship between the dictionary record and the performance records. In this example, the data that is defined by Dictionary Entry 3 has been excluded, so there is no field connector value for it and it does not appear in the performance records.

How the string of field connectors is constructed

When CICS is initialized, a unique connector value is assigned to every dictionary entry. CICS then examines the MCT entries for this run to see if you have excluded any system-defined performance data. If you have, the offset values for their corresponding dictionary entries are set to X'FFFF'. CICS then constructs a sequence of field connectors that excludes those with offsets of X'FFFF'. In this way, the connectors tell you which system- and user-data fields are going to occur in your performance records for this run. If you have not excluded any system-defined performance data, there is one field connector for every dictionary entry.

Note the difference between field connectors, field identifiers, and field offsets:

Field connectors: link the fields in a performance record with their dictionary entries. They are unique values that are assigned at initialization time. They may, therefore, change from one run of CICS to the next.
Field identifiers: allow you to exclude specific system-defined performance data from being collected during a CICS run. They are unique within a group name and record type, and they do not change between CICS runs. There is more information about field identifiers in Monitoring control table (MCT).
Field offsets: in the performance record allow you to build a table for fast selection of required fields in your monitoring data processing programs.