iucvsevr

Guidelines and Cautions

For additional information concerning IUCV and CMS IUCV support, refer to your VM system's IBM documentation, which covers many topics relevant to IUCV communication including communication with CP system services, user environments, and specific details on the CMS support of IUCV functions.

In using SAS/C IUCV functions, be aware of the following points:

You must first call the signal or sigaction function with the SIGIUCV signal as the first argument. This is necessary to establish signal handling before an IUCV signal occurs. You must do this before any IUCV function is called.
Each call to iucvset creating an IUCV path must be matched with an eventual call to iucvclr destroying the path. If, at program termination (either by return or exit ), there are still IUCV paths that have not been destroyed via iucvclr , the library issues iucvclr calls for these paths. Invoking iucvclr also frees the space allocated by iucvset for queuing interrupts.
Interrupts trapped by the library but not handled at program termination disappear with no effect.
If the value of the code argument in the iucvsevr function is not "ALL" , "ONE" is assumed.
As discussed earlier in the section on signal handling and message processing, you must be prepared to handle IUCV interrupts at all times. Each time a SIGIUCV signal occurs, you must reinstate signal handling before another signal occurs. In other words, the program must be prepared to handle interrupts as soon as iucvset is called. If there are times when you do not want to be interrupted, use sigblock and sigpause .
The examples in this section show the use of sigpause to wait for an IUCV signal. The use of sigblock to block the SIGIUCV signal at other times is critical to these examples. If you do not use sigblock (or sigsetmask ) to block IUCV signals, an expected signal may be discovered before the call to sigpause . In this event, sigpause causes the program to wait for a second signal. Depending on the logic of the program, this can cause it to wait for an indefinitely long period.
The maximum number of paths available to your program is returned in the integer addressed by the second parameter to iucvset .
Although there is no limit on the number of interrupts in the library queue, storage allocated by the library for its queue is not freed until the associated message path is terminated by a call to iucvclr or by program termination. The library uses approximately 44 bytes per enqueued IUCV message. Queue storage is allocated in 4K blocks. If the library cannot allocate a 4K block to extend the queue, then a user ABEND 1228 is issued.
None of the IUCV functions issue messages or set the errno variable. If, during program termination, paths are cleared implicitly by the library and an error occurs, an informatory NOTE is issued. However, the program cannot be informed that an error has occurred.

For more information on handling program interrupts and communications, refer to Chapter 5 of SAS/C Library Reference, Volume 1.

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