Empress Persistent Stored Modules
Empress Persistent Stored Modules (PSM) allow users to store
user-defined functions, operators, stored procedures and triggers in
the database, as objects in a schema. These objects can then be
invoked from SQL statement and application programs.
A Stored Procedure a procedural database object that
can be invoked by any client program.
Triggers are special types of stored procedures that get invoked
) automatically whenever certain events occur, and the
conditions satisfy. Traditionally, triggers have been associated
with database events such as insertions, updates or deletes.
PSM is a very useful enhancement of Empress RDBMS as:
- It can improve performance and can be used as a structuring
device for the application programs.
Quite often an application program performs a fair number of
database accesses to produce a limited number of results. If
this program requires to be executed repeatedly in the
client/server environments, it can be time consuming because
of network overhead. It is more efficient to run this program
on the server side. One way to do this is to put the program
into a procedure and store into the database as part of schema
definition. This way, not only the performance gets improved,
but also the application programming becomes more structured.
- It is a powerful tool for extending the functions of RDBMS to
meet customer specific requirements.
Empress provides many functions and operators which
are included with the standard distribution.  However, when an
additional function is required to operate on the data, you
can extend the functions of Empress to fulfill your
specific needs through the User Defined Functions capability.
Persistent Stored Modules provide an easy interface to
incorporate user defined functions into RDBMS.