How to start the IMS control region

You usually start the IMS control region with a z/OS® START command from a z/OS system console.

If, depending on the size of your installation, you have an alternate system console for the IMS MTO, be sure the z/OS system operator relays all IMS messages (that is, those beginning with BPE, CQS, DFS, DSP, and DXR) to the IMS MTO.

If the z/OS system console is physically separate from the IMS MTO, you should have a local telephone or paging line to enable communication between the z/OS operator and the IMS MTO. The MTO should also have easy access to the operators responsible for DASD and tape units.

When the IMS control region is started, IMS issues two DFS1929I messages. Message DFS1929I lists the system parameters and their values defined for the IMS system. This information will help you understand the configuration of a particular system. Understanding the configuration will be helpful in diagnosing problems. The system parameters are also listed in the job log.

IMS issues message DFS1929I once during initialization and again when restart completes. The first DFS1929I message reflects the system parameter values that are defined in the DFSPBxxx PROCLIB member. The second DFS1929I message reflects the system parameter values that are actually in effect for the current execution of IMS.

For online IMS systems, the control region automatically starts the DBRC address space. If you are running an IMS DB/DC or DBCTL environment, you can specify LSO=S as an EXEC parameter for the control region to start the DL/I address space. The following rules apply:

• IMS initialization waits until there is a separate address space available for DBRC.
• You can start DBRC manually (if, for example, a JCL error prevented DBRC from starting).
• When you restart IMS, you can change the specification of LSO=; IMS does not use any prior specifications.

After the control region has started, the MTO enters an IMS command to start the system. Select one of three ways of starting IMS:

1. Cold start
2. Warm start (also referred to as normal restart)
3. Emergency restart

Your operating procedures should include guidelines for the MTO in selecting the right type of startup.

You can alternatively use automatic restart instead of having the MTO enter an IMS command to restart the system. Specify AUTO=Y in the control region JCL to request automatic restart. IMS selects a suitable checkpoint for restart and notifies the MTO. You cannot use automatic restart if you:

• Want to perform a cold start
• Need to specify any options on the restart command (such as formatting system data sets, changing security options, or restarting only one portion of a DB/DC system)
• Need to override DBRC after a failure in which DBRC is unable to mark the subsystem record in the RECON data set as abnormally terminated, such as in the case of a power, CPC, z/OS, or DBRC failure