IBM System/390 software -- TPF System Technical Newsletter
TPF persistent collections support is a database manager service for application programs that
access TPF persistent collections on a TPF database. Persistent collections are abstract
representations of data that maintain their state beyond the life of the entry control block (ECB) that
creates them. Persistent collections support provides three collection lifetimes: long-term,
short-term, and temporary. Persistent collections support transparently integrates database
functionality with the application program and TPF does not need to have any knowledge of the
format of the data.
It is extremely important to be able to use a single, client-level application programming interface
(API) for saving and managing data regardless of how that data is physically stored on the
database. Most companies store their critical data in several different types of databases. Programs
that store and access this data need to be aware of the format that the data is in, which potentially
limits code reuse and restricts the data format from changing. With a TPF persistent collections
database, applications can essentially access and manage the data without the TPF 4.1 system
having any knowledge of the contents of the data stored. Furthermore, the TPF persistent
collections APIs can be called directly from C and C++ programs.
The TPF persistent collections database consists of user-defined components known as data
stores. Each data store can contain multiple collections with several different abstract collection
types available in the TPF persistent collections collection library. Each collection consists of zero
or more related elements that contain data. The data in each element may be a primitive data type,
a structure with subfields, a binary string, a reference to a TPF file, another persistent collection, or
even an object.
To increase the productivity of application programmers, TPF persistent collections support
provides:
In addition to implementing the collection types efficiently and reliably, TPF persistent collections
support provides the following benefits:
The collection library enables you to choose the appropriate abstract collection type for a given
condition by providing collections that are complete, systematic, and have a consistent combination
of basic properties. These properties help you to select abstract collection types that are at the
appropriate level of abstraction. For example, in a particular application you may have the choice
between using a bag or a key bag collection. Abag is an unordered collection of zero or more
elements with no key. Akey bag is an unordered collection of zero or more elements that have a
key. The properties of these two collections will help you decide which one is more appropriate.
Special and Lowercase Characters
TPF 4.1 no longer translates special and lowercase characters in output messages into periods (.)
for the following functional messages:
If you have workstations that do not support special or lowercase characters, translate the output
into characters that your workstations do support by using the UCCWTOP user exit. This is very
important because sending output to a workstation in a format that the workstation does not
support can cause unpredictable results. For more information about special characters, seeTPF
Programming Standards.
For more information about TPF persistent collections support, see the following publications:
Watch these pages for future articles about TPF persistent collections support.