In the context of ring processing, quiescing a system means removing it from the ring. The system can continue to run, but it cannot access or free global resources. Quiescing a system is normally done as the first step in removing a system from the complex.

To quiesce a system, the operator on the system to be quiesced (or on any active system that can communicate with the system to be quiesced) can issue the VARY GRS(sysname),QUIESCE command. A quiesced system is no longer part of the ring; it is, however, still known to the other systems in the ring.

Thus, quiescing a system is an action that you should take very seldom and for as short a time as possible. It might, for example, be part of the process of physical reconfiguration. When it is necessary to quiesce a system, the operator must first bring work on the system to an orderly shutdown. This procedure minimizes ring performance problems and data integrity exposures if the system is to be purged from the ring.

Global resource serialization, in response to the VARY GRS(sysname),QUIESCE command, places the target system in a quiesced state and forms a new ring without the quiesced system. The operators can use the global resource serialization messages (ISG011I and ISG013I) and, if necessary, D GRS, to verify that the system is now quiesced.

Global resource serialization can build a new ring without the quiesced system only when the links needed for the new ring are available. When the complex is fully-connected and alternate links are available, rebuilding the ring without the quiesced system is not a problem. If a link that it needs to build a new ring without the quiesced system is missing, global resource serialization rejects the VARY GRS(sysname),QUIESCE command. After enabling the required links, the operator can enter the command again. Once the system is quiesced, it can either rejoin the ring, which does not require a reIPL, or be purged from the ring.