External subsystem trace

The External Subsystem (ESS) trace entries help you analyze problems for either:

• A connection problem between the IMS control region and the external subsystem (for example, Db2 for z/OS®)
• Any problem between the IMS dependent region and the external subsystem

The following figure illustrates the external subsystem (ESS) trace record format. Each of the sixteen words is 4 bytes long. Words 0 and 1 hold the standard ESS trace record prefix. The Module ID and Sub function (WORD 1) determines what information appears in words 2 through 15.

Figure 1. External subsystem (ESS) trace record format

where

represents

I

This 1-byte field contains the hexadecimal trace record ID. Two possible ID values are X'57' and X'58'. The X'57' record ID is created by a module that executes in the IMS control region (for example, the ESS mother task DFSIESI0). The X'58' record ID is created by a module that executes in an IMS dependent region (for example, DFSESCT0).

R

This 1-byte field is reserved.

SEQ NUM

This 2-byte field contains the hexadecimal trace record sequence number assigned by the IMS trace component.

MOD ID

This 2-byte field contains a hexadecimal value that identifies the module that created the trace record. Each ESS module has an associated module ID. Macro DFSESFC contains the complete list of IDs.

SUB FUNC

This 2-byte field contains a hexadecimal value that identifies the subfunction that created the trace record within the module. For example, if a module creates a trace record in each of five internal subroutines, each subroutine has a unique SUB FUNC ID.

The following table shows:

• The ID of the module that created the trace record
• The ID of the subfunction (within the module) that created the record
• The name of the module that created the record
• A description of the event being traced