User guide

Writing ENFORM Servers
ENFORM Servers
7–6 058058 Tandem Computers Incorporated
Message Protocol and
Descriptions
The dialogue between processes is structured by a protocol that includes a startup
message, an OPEN message, request and reply messages, and a CLOSE message. The
messages transferred between processes to create, use, and terminate an ENFORM
server are described below in the sequence of the protocol.
Startup Message—The Command Interpreter startup message is sent to a process
(an ENFORM server) when the process is successfully created. The startup
message is used to define ENFORM server characteristics such as: the number of
simultaneous requesters per server and the time period the ENFORM server waits
before terminating, if there is no requester. One startup message is sent per
ENFORM server creation. (For more information, refer to the GUARDIAN
Operating System Programming Manual Volume 2, Command
Interpreter/Application Interface section.)
OPEN Message—The OPEN message is a File Management Procedure used to
establish a communication path between two processes; that is, the query
processor and an ENFORM server. One OPEN message is sent per ENFORM
server session. If you specify an exclusion mode via an ASSIGN command, that
exclusion mode is passed in the OPEN message.
Initialize Message—The initialize sequence is a pair (a request and a reply) of
messages between the query processor and an ENFORM server. The initialize
messages associate a query processor with an ENFORM server and describe the
environment in which the ENFORM server performs. The query processor sends
one initialize message sequence for each set of requests to an ENFORM server.
More than one initialize message can be sent per ENFORM server OPEN message.
Request Message—The query processor sends a request message to an ENFORM
server to ask for a data record and the server replies with the record or an
indication that there are no more records. The request message can contain data,
end-of-file or error information. The query processor can send many request
messages per ENFORM server session.
Terminate Message—The terminate sequence is a pair (a request and a reply) of
messages between the query processor and a server. The terminate message
indicates there are no more requests for an ENFORM server. The query processor
sends one terminate message per set of requests. More than one terminate
message can be sent per ENFORM server OPEN message.
CLOSE Message—The CLOSE message is a File Management Procedure used to
terminate access to an ENFORM server. The CLOSE defines the end of use by the
query processor and the end of an ENFORM server session. The query processor
sends one CLOSE message per OPEN message.
The entire sequence of messages from OPEN through CLOSE can be performed for an
ENFORM server more than once per query execution.