SNAX/HLS Application Programming Manual

4 The Standard Verb Interface
104707 Tandem Computers Incorporated 4–1
SNAX/HLS uses a verb concept to allow any program in a Tandem system or network
to communicate requests to SNAX/HLS. Verbs are executed and then status is
reported with a return code and modifiers. This section discusses return code
categories, verb processing, and verb formats.
Verb Processing All communication to SNAX/HLS involves a WRITEREAD procedure. The WRITE
portion of the I/O process delivers the request and optional data to the SNAX/HLS
process. The request is screened through a series of checks to verify that the request
can be satisfied. The READ portion of the I/O delivers a reply that has a standard
header plus other indicators (the number and type of indicators vary with individual
reply). In the standard reply header, the RETURN-CODE field indicates the status of
this particular request.
For some verbs, a user option, called COMPLETION-MODE, allows the application to
specify when the response to a request is to be generated. The three options are
immediate, wait, and queued. These are outlined below.
Immediate Completion
Mode
In the immediate completion mode, SNAX/HLS returns control as soon as the
SNAX/HLS server has checked the request for validity. The immediate mode is
available on the HLS-ALLOCATE, HLS-CALL-USER, and HLS-OPEN verbs. The flow
of an immediate verb is shown in Figure 4-1.
Figure 4-1. Flow of an Immediate Operation
USER SNAX/HLS
:
:
develop verb+msg
:
:
CALL WRITEREAD
syntax checks
resource checks
fsm checks
state checks
(read completes)
:
:
INTERPRET VERB RETURN CODE
: