Queue structures
A queue structure is a coupling facility list structure that contains a collection of data objects, some of which might have the same name. Data objects that have the same name are considered to be on the same queue.
Queue structures support structure overflow, in which an associated overflow structure can be allocated to prevent the queue structure from becoming full. A primary queue structure and its associated overflow structure are known as a structure pair.
CQS physically divides the queue structure list headers into 11 private queue types for CQS use and 11 client queue types for client use. Client queue types are defined by the client. A client can group queues associated with a type of work, such as transactions. A queue type can have a value of 1 to 255. Any queue type over 11 is mapped into one of the physical queue types.
CQS manages private queues and client queues on queue structures. CQS uses the private queue types to manipulate client data objects for CQS requests. Each client queue type can be used by a client for a different type of work. A client registers interest in only those queue types that it can process, based on the types of work you define for it.
Private queue types managed by CQS
The following table shows five of the private queue types, and the work that a client processes on them.
| Queue type | Description |
|---|---|
| Cold queue | Contains data objects that are in doubt for a client or for a CQS that cold started |
| Control queue | Contains control list entries that CQS uses to manage list structures and control processes (such as structure checkpoint and structure recovery) |
| Delete queue | Intermediate queue used for CQSDEL request processing |
| Lock queue | Contains data objects that are locked by the CQSREAD request |
| Move queue | Intermediate queue used for CQSMOVE request processing |