Introduction to ENFORM

Transferring Control to the Query Processor
How ENFORM Works
3–4 058051 Tandem Computers Incorporated
Transferring Control to
the Query Processor
The query processor is a server process that interprets the compiled query and
accesses the database to build a target file. The process can occur in one or both of the
following forms:
1. As a named server process that can be shared (sequentially) by several ENFORM
processes. This type of server is persistent (it exists until it is stopped), has a
backup process, and handles queries one at a time. To start this type of server, the
system manager uses the QP command and the Command Interpreter commands
ASSIGN and PARAM. Your ENFORM program can then access it by specifying
its name in an ?ATTACH command.
2. As a dedicated server process that is created for and provides service to an
individual ENFORM process; this process is created each time an individual
ENFORM program is run.
There are two reasons for using named query processors instead of dedicated query
processors.
First, they maximize effective use of the system resources that are being shared by all
applications in your installation. Starting and stopping dedicated processes is
generally an expensive use of resources; it should be avoided whenever possible.
Additionally, you can balance the system load by moving the named server to a lightly
loaded CPU to increase its performance or off a heavily loaded CPU to increase the
performance of other processes running on that CPU.
Second, they can be used for efficient processing of network distributed queries as
discussed in Section 1. Simply start the query processor at the network node where
most of the data resides.
Dedicated query processors, of course, will generally process an individual query
quickly because they are not shared.