Cisam

cisam, or C-ISAM, is a X/Open Standards-compliant, (C-programming-language Index Sequential Access Method).

Description

First created by Informix in the 1980's and bought by IBM in +- 2000, it is an API (Application Programming Interface) of C-language functions for managing data files organised in a B+ tree-index scheme. It provided one of the major building blocks for the massively popular first generation Informix RDBMS (Relational Database Management System), which allows data manipulation by way of the SQL (Structured Query Language) protocol. This version later became known as the (SE) Standard Engine, when the cisam layer was improved in the RDBMS. By bypassing the "cooked" file-system of the operating system, the improved verson accessed "raw disk". Informix called this the "Turbo" engine, in line with many other products, which adopted the popular "Star Wars" concept for improving the speed of a "star fighter". This name quickly became associated with being a "cheap", "bolt-on" type of modification rather than the engineering breakthrough that it was and the name was abandoned in favour of the name "On-Line™".

History

Many systems were written using cisam, which was fast and efficient and flexible, while providing effective mechanisms for maintaining data integrity. Mostly business applications used cisam. These systems were written in "C", which is a low level 3GL. For business purposes, development in "C" was too slow and error prone, requiring very high skill levels. Informix addressed this by the introduction of 4gl. This allowed the programmers to focus on the business logic, while the compiler and RDBMS took care of error checking and data-type conversion and most importantly, memory management. Thus, the direct use of cisam, as a product declined, while 4GL with embedded SQL, became the new darling of business programmers. Unfortunately, Informix made some strategic errors by not adapting to the next generation of "Visual" or "GUI based" programming tools. Competitors like Microsoft and Oracle suppplanted these products by vertically integrating theirs and Informix focused on the RDBMS. The new application of these products went into decline with the company. In 2006, they are still in wide use round the world and are also available and supported.