HP-UX SNAplus2 R7 APPC Programmer's Guide

Concepts

Non-Blocking Operation

a multi-threaded TP that issues APPC verbs from more than one thread. To issue a verb in non-blocking mode, the

TP sets an option in the

opext parameter of the verb, as described in Chapter 4, APPC Conversation Verbs.

For each TP and conversation, APPC provides a number of queues on which verbs can be held while waiting to be

processed. Each queue handles a different subset of the valid APPC verbs, so that each verb is associated with a

different queue.

• If the TP issues a verb and there are no verbs already being processed for the appropriate queue, the verb is

processed immediately.

• If the TP issues a non-blocking verb and another verb is already being processed for the appropriate queue,

the verb is added to the queue (behind any other verbs already waiting on the appropriate queue). It will be

processed after the verbs already queued have completed (except for the Allocate queue, as described below).

• If the TP issues a blocking verb and another verb is already being processed for the appropriate queue, the verb

is rejected with an error return code.

The queues available to the TP, and the verbs that each queue handles, are as follows.

Allocate queue

For each active TP, there is a single queue that handles the following verbs:

• [MC_]ALLOCATE

• [MC_]SEND_CONVERSATION

Two or more verbs on this queue can be processed at the same time, so they are not guaranteed to complete

in the same order in which they were issued.

Send-Receive queue (half-duplex conversations only)

For each active half-duplex conversation, there is a single queue that handles the following verbs:

• [MC_]CONFIRM

• [MC_]CONFIRMED

• [MC_]DEALLOCATE

• [MC_]FLUSH

• [MC_]PREPARE_TO_RECEIVE

• [MC_]RECEIVE_AND_WAIT

• [MC_]RECEIVE_IMMEDIATE

• [MC_]SEND_DATA

• [MC_]SEND_ERROR

The [MC_]RECEIVE_AND_POST verb is not held on this queue. This verb cannot be issued, in either

blocking or non-blocking mode, if any of the Receive verbs is already being processed for the conversation.

Send queue (full-duplex conversations only)