Transmission Control Queue Considerations

Review the following Transmission Control Queue considerations before installing the product:

  • Because of the changes in the Transmission Control Queue (TCQ) to support Processes containing up to 1 MB, review all SUBMIT exits. Modify any SUBMIT exit that:
    • Alters the size of the TCQE (change TQRECLN)
    • Uses TQCSPRD (pointer to first, that is, current step)
    • Uses TSHFTCQE (forward pointer to next step)
    • Uses TSHBTCQE (backward pointer to previous step)
    • Adds or changes PACCT or SACCT information

      The TQCSPRD, TSHFTCQE, and TSHBTCQE fields contain offsets relative to the start of the TCQE for Processes that do not exceed 64 KB. For larger Processes, these fields must be multiplied by 16 before being used as an offset. In the TCQE, a flag indicates whether or not this processing should take place (the flag byte is TQFLAGA and the bit equate is TQGT64K).

      SUBMIT exits are no longer allowed to change the size of the TCQE (modify TQRECLN). The sample SUBMIT exit DGAXACCT previously showed how to add the PACCT and SACCT fields to the end of the TCQE and extended the length. Because this is no longer allowed, fields have been reserved for the PACCT and SACCT information to allow the SUBMIT exit to add or modify accounting information as required. The sample SUBMIT exit DGAXACCT has been modified to show you how to manipulate this account information.

  • Using IGGCSI00 to access files requires READ access to the master catalog.
  • Only Version 2 Flows, which are used for the TCP/IP and SNA LU6.2 protocols, support the ability to checkpoint files larger than 4 GB. Version 1 Flows, which were used for VTAM SNA LU0, do not support this ability.
  • To honor the permission setting for HFS files using the PERMISS keyword, you must set the z/OS UNIX System Services UMASK to 000 either by default or by using the runtime environment variable, _EDC_UMASK_DFLT. To set the environment variable, define the _EDC_UMASK_DFLT=000 variable in a RECFM=VB type file and allocate the ENVIRON DD in the IBM® Connect:Direct® startup JCL.