Within the CICS Execute Interface Block EIB, which field identifies the last CICS command executed by the task?

Introduction / Context:
The Execute Interface Block, or EIB, is a control block that CICS provides to each task. It contains fields describing the current environment, such as transaction id, response codes, and timing information. One of these fields records the function code associated with the most recent CICS command, which is useful in debugging and in generic error handling routines. This question asks which specific EIB field serves that purpose.

Given Data / Assumptions:

• CICS builds an EIB for each task and makes it available to application programs.
• Several CICS commands may execute in a task, and the most recent one is often relevant when diagnosing errors.
• Different EIB fields carry different pieces of information such as transaction id, terminal id, response codes, and command function codes.
• The question asks for the field that identifies the last CICS command executed.

Concept / Approach:
EIBFN is the field in the Execute Interface Block that holds the function code of the last CICS command executed. This function code is a numeric value that corresponds to an internal code for commands such as READ, WRITE, LINK, or XCTL. Error handling routines sometimes examine EIBFN in combination with response codes to decide how to recover or log information. Other EIB fields have different roles, such as EIBTRNID for transaction id and EIBRESP for response codes, so they are not used to identify the command itself.

Step-by-Step Solution:
Step 1: Identify that the question concerns the last CICS command executed, not the transaction id or response code. Step 2: Recall that EIBFN is documented as the function code field that represents the last CICS command executed. Step 3: Compare EIBFN with other EIB fields such as EIBTRNID, EIBRESP, and EIBTIME, which serve other purposes. Step 4: Choose the option that correctly names EIBFN as the field for the last command function code.

Verification / Alternative check:
CICS reference materials list EIBFN as the function code field and provide tables mapping numeric values to specific commands. Debugging guides often recommend checking EIBFN when analyzing abend dumps to see which command was running when a failure occurred. In contrast, EIBTRNID is consistently documented as containing the transaction id, and EIBCALEN as containing the COMMAREA length, which confirms that they are not the right answers for this question.

Why Other Options Are Wrong:
Option B incorrectly claims that EIBTRNID holds the last command, but EIBTRNID actually stores the transaction identifier. Option C is wrong because EIBRESP holds numeric response codes, not the command itself or its full text. Option D misuses EIBTIME, which records the time the task began, not command information. Option E is incorrect because EIBCALEN indicates the length of the communication area, not the last CICS command executed.

Common Pitfalls:
A common pitfall is confusing EIBFN with EIBRESP and assuming the response code alone identifies the failing command, which is not always the case. Another issue is failing to save EIBFN early in a generic error routine if it may be overwritten by subsequent CICS calls. Understanding the role of EIBFN allows developers and support teams to interpret dumps and logs more accurately and to trace errors back to the correct CICS command.

Final Answer:
EIBFN contains the function code that identifies the last CICS command executed by the task