IMS Logging

While IMS is running, it records the event information that is necessary to restart the system if a hardware or software failure occurs. The event information is recorded on an online log data set (OLDS).

When an OLDS is filled, or some other event causes IMS to switch from one OLDS to another, it is archived to the system log data set (SLDS). There is a finite number of OLDS data sets, although this number can be dynamically changed, which are pre-allocated and defined to the IMS control region. The OLDS are reused during the duration of the control region. There can be an infinite number of SLDSs, which are created and allocated as needed.

Related Reading: For more information, see Chapter 22, "IMS Logging," on page 367.