Subsystem Control Point (SCP) Management Programming Manual

SPI Programming Considerations for SCP

Subsystem Control Point (SCP) Management Programming Manual—520619-001

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Data Definition Files

The tokens, values, and other data items necessary to use SPI to manage an SCP process

are contained in files with names of the form:

ZSPIxxxx (Subsystem Programmatic Interface definitions)

ZCOMxxxx (common communications subsystem definitions)

ZCMKxxxx (common subsystem definitions)

ZSCPxxxx (Subsystem Control Point definitions)

ZTRCxxxx (tracing definitions)

where xxxx represents a specific development language:

C (C)

COB (COBOL)

DDL (Data Definition Language, from which the other files are derived)

PAS (Pascal)

TACL (Compaq Tandem Advanced Command Language)

TAL (Transaction Application Language)

For a particular category of definitions (ZSPI or ZSCP, for instance) the language-

specific files are all generated from one file containing definitions expressed in

Compaq’s Data Definition Language. This file has a language code of DDL. Thus, the

file ZTRCDDL is the source file for the definition files ZTRCC, ZTRCCOB, ZTRCPAS,

ZTRCTACL.

These files are commonly found on the operating system software release volume in the

subvolume ZSPIDEF but can be stored elsewhere by system management.

SCP Command-Message Processing

These subsections describe specific aspects of SCP’s role in SPI message processing.

Support for Concurrent Opens and Openers

An SCP process can support a maximum of 1000 communications management

applications and a maximum of 256 communications subsystems at any one time.

Message Buffer Size

When sending command messages to (rather than through) an SCP process, the message

buffer in your application should have a length of ZSCP-VAL-BUFLEN. This buffer

should be adequate for most command messages and responses. The structure ZSCP-

DDL-MSG-BUFFER is available for allocating a buffer of this size. To accomodate

larger requests or responses, you can use a buffer length of ZSCP-VAL-MAXBUFLEN.

Command-Message Routing

An application that routes messages to or through an SCP process must include the

identity of the destination subsystem manager process in the message, either by

including it as part of the object name assigned to ZCOM-TKN-OBJNAME or by