Making IMS ready
IMS must be made ready to receive VTAM® logon (session initialization) requests. Ready IMS by issuing the IMS /START command with the DC keyword.
The /START DC command tells VTAM to pass any queued VTAM logon requests (and any logon requests for workstations known to VTAM as belonging to IMS) to IMS.
- Initiates IMS Transaction Manager processing
- Opens the VTAM access method control block
- Enables the IMS VTAM logon exit
Any logon requests received by VTAM before the IMS /START DC command is issued, but after the IMS VTAM access method control block (ACB) has been opened, are queued in VTAM until the /START DC command processing is completed. If VTAM is active when IMS is initialized, and the DFSDCxxx PROCLIB member keyword VACBOPN=INIT, then the IMS VTAM ACB is opened. If DFSDCxxx PROCLIB member keyword VACBOPN=DELAY, then the IMS VTAM ACB open is delayed until the /START DC command is processed.