Premium Content

Get Premium Content and take advantage of the full potential available in Stories, Links and the Download Area.
Register as a regular user, it's free, and become a community member, share your knowledge or start promoting Cobol in open source.

Topics

User Functions

Older Stories


Welcome to myCobol.net Friday, 23 June 2017, 07:15 @ CEST

Audio-Visual Resources System (AVR)

Project StickleBack
  • Friday, 19 July 2013, 18:24 @ CEST
  • Contributed by:
  • Views:
    2,810
This system was designed to maintain a catalog of audio-visual media (16mm movies, video cassettes, filmstrips, and a variety of other educational media) for the office of a county superintendent of schools in California, US.

Donated to Project Stickleback, 2013-05-18.
The complete and original Cobol sourceText and a demo database are available in the downloads area for community members. You're invited to register, it is free. Read more for a extensive description.

In their day, these media were quite expensive, so the county superintendent would purchase and maintain them for sharing and circulation among the subordinate school districts in the county. To support this sharing, the system also provided the capability to receive requests for media items from teachers and schedule them for delivery to the schools based on dates specified by the teachers and the availability of individual media items. It was common to have multiple copies of the same "title," so the system managed these multiple copies (termed "items") and attempted to evenly rotate requests among them.

The system also maintained descriptive and library classification information about the media. It used this information to generate printed catalogs of the superintendent's collection, which were distributed to schools so that the teachers knew what titles were available and the identifiers necessary for ordering them. Initially, this catalog was prepared by creating a magnetic tape with semi-formatted text, which was sent to a service bureau for final composition on a Xerox 9700 laser printer. Later, when PC desktop layout software and inexpensive laser printers became available, this process was modified to download data to a PC for final layout and composition.

The system was originally designed in 1984 to run on a Burroughs B6900 computer system, using the DMSII database management system and the GEMCOS transaction manager. As the Burroughs B series systems morphed into the Unisys A Series, this system was adapted to the newer COMS transaction manager. It is still capable of running today on the current models of that architecture, Unisys ClearPath MCP systems.

The system was also originally designed and programmed for COBOL-68 using a COBOL macro preprocessor from PROGENI Systems (now PROGENI Corporation). PROGENI read a "spec" file consisting of macro calls and in-line COBOL coding, expanded the macros, and output a standard COBOL source file, which was then compiled. It was converted to COBOL-74 in 1985. After some years, the customer dropped their PROGENI license, at which point the system was maintained from the last set of generated COBOL sources. This explains the messiness and mixture of styles still visible in many of the programs.

Another historical facet of the system is that the original version was written very much in crunch mode in less than three months during the summer of 1984. The audio-visual department had to reduce staff due to budget constraints, but still had to service a few hundred thousand media requests per year from the schools. The automated scheduling mechanism proposed for this system was the only way to do that. The initial development was intended to be just a stopgap solution and a prototype for a more permanent design that would follow. Of course, that never happened, but the original design proved to be good enough and adaptable enough that it continued to be enhanced and used through the 1990s.

AVR is not Y2K-capable, although it would not be very difficult to make it so. The audio-visual department decided to replace AVR with a Linux-based solution that offered a web-based request interface. The production system was shut down in late 1999.

Today, this type of media cataloging and scheduling system is obsolete. In the early 1990s, schools became eligible to purchase duplication rights for VHS video cassettes, which made centralized acquisition and delivery of video media uneconomical. Instead of circulating videos between a central library and schools, the audio-visual department would simply make a VHS copy and send it to the school to keep. More recently, streaming distribution over the Internet has made even the duplication of physical media uneconomic. Nonetheless, AVR is a good example of a relatively small, COBOL-based system, with both on-line and background batch processes.

DMSII is not a relational database. It belongs to the networked/hierarchical family of database management systems. Its schema is specified by means of a language called DASDL, which is compiled into a canonical format called the DESCRIPTION file. The DESCRIPTION file is used to generate some software libraries tailored to the schema, and is used by the compilers to import data item and record structure information into the program. As a result, object programs are bound to the schema, and changes to the schema can generate a requirement that programs using the affected structures in the database be recompiled.

Documentation for the current Unisys MCP systems is publicly available from the Unisys support web site. Although the AVR system has not been actively maintained for over 12 years, documentation for the current Unisys systems is still relevant to AVR. See:

http://public.support.unisys.com/comm...aries.aspx

Under "ClearPath Servers and Software", click "System Software" and then "ClearPath MCP Software".

The following comments are owned by whomever posted them. This site is not responsible for what they say.