Performing a cold start

Under certain circumstances—for example, if an IMS goes down during an online change—you might need to perform a cold start. The process you follow to perform a cold start varies depending on whether the IMS uses local or global online change.

For general information about cold start, see Cold start in IMS Version 15.5 Operations and Automation.

Local online change and cold start

Using local online change affects all types of IMS system definitions. IMS online subsystems place control blocks in the IMS.MODBLKS staging library. Before you perform a cold start, copy the MODBLKS library to either the IMS.MODBLKSA or the IMS.MODBLKSB data set.

If you copy these data sets to the inactive library, update the IMS.MODSTAT data set to change the IMS.MODBLKS data set DD name. If you copy to the active library, you cannot, in case of problems, return to the last system environment before the change.

Global online change and cold start

Attention: Typically, an IMS that was down during a global online change needs to be cold started when it comes back up. A cold start might be required to prevent restart from processing log records against the current online change libraries, potentially causing restart to fail or resulting in a severe error later.

Before the first IMS in the IMSplex cold starts the first time, you must initialize the OLCSTAT data set. To initialize the OLCSTAT, use the Global Online Change utility (DFSUOLC0).

Important: Use the Global Online Change utility with caution, so you do not inadvertently destroy valid OLCSTAT data set contents. If you do destroy valid OLCSTAT data set contents, global online change and initialization of additional IMS systems fail until the OLCSTAT data set is re-initialized.

You should establish an OLCSTAT data set recovery procedure to deal with the loss of the OLCSTAT data set. After every successful global online change, record the modify ID, the active online change library suffixes, and the list of IMS systems that are current with the online change libraries. If the OLCSTAT data set is destroyed, run the initialize function of the Global Online Change utility with the saved data to re-initialize the OLCSTAT data set.

Related reading:  For more information about the Global Online Change utility, see IMS Version 15.5 System Utilities.