Managing CMAS restarts

When you restart a CMAS in a CICSplex environment, the restart might be a cold or warm start, depending on whether the data spaces that the CMAS used previously still exist. You should be aware of the circumstances under which a cold or warm start occurs and the difference between cold and warm starts.

When the CMAS starts, if no data spaces that the CMAS used the last time it was active still exist, the start is a CMAS cold start; if such data spaces exist, the start is a CMAS warm start.

Note: You cannot specify whether the restart of a CMAS is a cold or warm start. The CICS® START system initialization parameter does not affect the restart of a CMAS in a CICSplex.

The CICSPlex® SM data spaces are associated with CICSPlex SM components. There are two types of CICSPlex SM data spaces:

Private data spaces
Data spaces that are used by the CMAS only
Shared data spaces
Data spaces that are shared with both the MAS and batch API address spaces that connect to the CMAS
Table 1. Types of CICSPlex SM data spaces and associated components. The table lists, by the data space type, CICSPlex SM components and the associated data spaces. In the table, x in the data space prefix is a number ranging from one up to the number of data spaces that are allocated for the component. The Data Cache Manager component has only one data space. The data space names are all suffixed by the CICS SYSIDNT parameter for the CMAS.
Type of data spaces Component name Data space prefix
Private
  • Business Application Services
  • Communications
  • Monitor Services
  • Real-time analysis
  • BASx
  • COMx
  • MONx
  • RTAx
Shared
  • Data Cache Manager
  • Data Repository
  • Managed Application System
  • Queue Manager
  • Topology Services
  • Workload Manager
  • DMDS
  • DATx
  • MASx
  • QUEx
  • TOPx
  • WLMx

When does a CMAS warm start occur

When a CMAS terminates, private data spaces are deleted, but shared data spaces are deleted only when no encumbrances are held on the shared data spaces. If the shared data spaces still exist by the time the CMAS is restarted, a CMAS warm start occurs.

When each MAS or batch API address space connects to the CMAS, the MAS or batch API address space has access to and holds an encumbrance on the shared data spaces.

For a MAS, the encumbrance lasts until the MAS is terminated or until the MAS agent within the MAS is terminated.

For a batch API address space, the encumbrance lasts until the batch API address space terminates, or until every thread that is created by the address space is either disconnected by the EXEC CPSM DISCONNECT command or terminated by the EXEC CPSM TERMINATE command.

If any MAS or batch API address space encumbrances exist when the CMAS terminates, the shared data spaces are not deleted. If the encumbrances still hold when the CMAS is restarted, the restart is a warm start.

When does a CMAS cold start occur

If no MAS or batch API address space encumbrances exist when the CMAS terminates, both the private and shared data spaces are deleted upon the termination of the CMAS. Any subsequent CMAS start is a cold start because no data spaces are active.

If there are encumbrances on the CMAS but the encumbrances end before the CMAS is restarted, the restart is a cold start.

What is the difference between a cold start and a warm start

For a cold start, the CMAS creates both the private and shared data spaces. For a warm start, the CMAS creates the private data spaces, retains the DMDS, DATx, WLMx, and MASx shared data spaces, but deletes and re-creates the QUEx and TOPx shared data spaces.

Generally, it does not matter whether a CMAS restart is a cold or warm start.

The CICSPlex SM system parameter CACHEDSNUM can be changed only on a CICSPlex SM CMAS cold start.

How do you ensure that a CMAS cold start occurs

If you need to perform a CMAS cold start, you must ensure that the data spaces for the CMAS no longer exist before starting the CMAS. So, after the CMAS, the connected MAS regions, and all batch API programs are terminated, issue the MVS display job command for the Environment Services System Services (ESSS) address space on the LPAR. With this command, you can verify that the WLM data spaces are deleted. The format of this command is as follows:
 D J,EYUXvrm
where vrm is the CICSPlex SM release number of the CMAS. For example, for CICSPlex SM V5R6M0, the command is D J,EYUX560. This command shows the data spaces for the specified CICSPlex SM release on that LPAR.

To know what encumbrances exist for a CMAS, run the CICSPlex SM EYU9XENF utility. This utility displays all CMASs that are connected to the ESSS, even though some might have already terminated. For each listed CMAS, this utility also displays the MAS and API address spaces that are still connected to the shared data spaces of the CMAS.