The command buffer for IKJEFLD1 or input buffer for IKJEFLD contains the information the user entered when logging on, including the LOGON command. For example, if the user entered LOGON USER1, the command or input buffer would contain LOGON USER1.

The logon processor obtains the buffer and passes it to the exit. The exit can alter the command or input buffer. If IKJEFLD alters the input buffer, it must update the current length of the data in the parameter. However, IKJEFLD must not change the maximum length of the parameter. See Parameter list for IKJEFLD.

IKJEFLD1 changes the command buffer it receives and updates the length field (parameter entry 1 in TSO/E standard exit parameter list) to specify the length of the updated command buffer.

If an ABEND occurred and the logon processor is retrying, the logon processor may pass a buffer length of zero to the exit. If there is a JCL error, the logoff processor may call the exit and pass a buffer length of zero.