At IPL time messages, TSS2000I, TSS2001I and CAS2031I are issued and TSS is even not started yet.
What makes those messages get issued?
Does TSS fully activate after those messages are issued?
To answer to those questions, we need to review z/OS IPL phases briefly.
The IPL (Initial Program Load) phases are mainly:
The hardware process of loading z/OS, the HARDWARE IPL.
The loading and initialization of the nucleus, the IPL RIMs. (Resource Initialization Module)
The initialization of general system resources, the NIP RIMs. (Nucleus Initialization Phase)
Master Scheduler Initialization, the MSI initialization
Let's have a look at MSI in more details because it's during this phase that the z/OS security is started.
All IPL processing is now complete.
When security is started modules, ICHSEC00, ICHSEC05, ICHSCDMY are involved. All are aliases of SAFRTSEC and must reside in LPA.
Module SAFRTSEC, which:
When all is done, TSS is ready to be started and security is fully available when TSS is up and running.
Release: TOPSEC00200-15-Top Secret-Security