OSI/MHS P7 Application Programmatic Interface (P7 API) Manual

Introduction to the P7 API

OSI/MHS P7 Application Programmatic Interface (P7 API) Manual—424825-001

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The P7 API

The P7 API product is Compaq’s implementation of an API that provides the services of

a P7 message store access protocol. The P7 protocol is the means by which an X.400

user agent submits messages to and retrieves messages from the message store of an

X.400 message handling system (MHS).

Although the Compaq P7 API is not based on any X.400 API standards, it is modeled

after X.229: Remote operations: protocol specification, in Recommendations X.220-

X.290 (1988). The P7 API enables client applications to access the services associated

with the P7 protocol. It acts as a conduit that transfers PDUs containing P7 encoded

operations data between a client application and the OSI/MHS subsystem. Client

applications written using the P7 API procedures can perform P7 operations on

messages in the message store without using the services of the underlying OSI layers.

The following subsections describe the P7 API components and the OSI/MHS

components used by the P7 API.

P7 API Components

The P7 API consists of a procedural interface, external declaration files used by the

client application to access the procedures, and a P7 API object file. The interface

includes procedures to initialize the environment, begin and end sessions, and perform

P7 operations. The external declarations contain definitions of the parameters in the

procedures. The object file contains the executable code for the P7 API procedures.

You can call the P7 API procedures from programs written in the C language or in the

Transaction Application Language (TAL) if the TAL program is called from a C main

program. Declaration files are provided in TAL and C.

You can include the declaration files in the client application when the application is

compiled. You can either bind the P7 API object file into the client application when

the application is compiled or bound, or you can treat the P7 API object file as a user

library file that is used to resolve undefined externals at run time. For more information

on creating an executable program, see “Creating an Executable Program” in Section 2.

OSI/MHS Components Used by the P7 API

When you call a P7 API procedure from your client application, the P7 API passes the

request for services to a local operations (LO) group in the OSI/MHS subsystem. P7

operations, such as LIST and FETCH, are then passed from the LO group to the

message store (MS) group servicing this user. P7 SUBMIT operations are passed from

the LO group to either the MS group or to the message relay (MR) group. Within the

OSI/MHS subsystem, the MHS manager process (MHSMGR) monitors and controls the

LO groups. Figure 1-2 shows these processes.

Note. The P7 API does not include the facilities to perform ASN.1 encoding and decoding of

the data sent to and received from the OSI/MHS subsystem; those facilities can be part of the

client application or part of any user code bound into the client application. If they are

contained in the client application, the client application must write the encoding and decoding

facilities by hand or use an ASN.1 compiler.