Temporary storage queues

Temporary storage is the primary CICS® facility for storing data that must be available to multiple transactions. Data items in temporary storage are kept in temporary storage queues. The items can be retrieved by the originating task, or by any other task, by using the symbolic name assigned to the temporary storage queue.

A temporary storage queue containing multiple items can be thought of as a small data set. Specific items (logical records) in a queue are referred to by relative position numbers. The items can be addressed either sequentially or directly, by item number. If a queue contains only a single item, it can be thought of as a named scratchpad area.

Temporary storage queues are identified by symbolic names of up to 16 characters. To avoid conflicts caused by duplicate names, establish a naming convention. For example, the operator identifier or terminal identifier could be used as a suffix to each programmer-supplied symbolic name. The fact that temporary storage queues can be named as they are created provides a powerful form of direct access to saved data. You can access scratchpad areas for resources such as terminals and data set records by including the terminal name or record key in the queue name.

Compared with other methods to pass data from task to task, temporary storage queues can require more processor use. You use an EXEC CICS command for every interaction with temporary storage queues, and CICS must find or insert the data by using its internal index. The processor use with main temporary storage is therefore greater than with the CWA or TCTUA. With auxiliary storage, there is typically data set I/O as well. Shared temporary storage pools require temporary storage servers, and applications must access the coupling facility to retrieve the data.

However, temporary storage queues have a number of advantages over other methods to pass data. You do not need to allocate temporary storage until it is required. You keep it only as long as it is required, and the item size is not fixed until you issue the command that creates it. Temporary storage queues are therefore a good choice for relatively high-volume data and data that varies in length or duration. Resource protection is also available for temporary storage queues.

Temporary storage queues remain in storage until they are deleted by the originating task, by any other task, or on an initial or cold start. Your application can use the DELETEQ TS command to delete temporary storage queues at the end of their useful life. If your application cannot always delete temporary storage queues, consider setting up automatic deletion. You can make CICS automatically delete non-recoverable temporary storage queues in main storage or auxiliary storage if they have not been accessed recently. The expiry interval in your TSMODEL resource definitions controls automatic deletion.