Page "Database management system" Paragraph 6

The Codasyl approach was based on the " manual " navigation of a linked data set which was formed into a large network.

When the database was first opened, the program was handed back a link to the first record in the database, which also contained pointers to other pieces of data.

To find any particular record the programmer had to step through these pointers one at a time until the required record was returned.

Simple queries like " find all the people in India " required the program to walk the entire data set and collect the matching results one by one.

There was, essentially, no concept of " find " or " search ".

This may sound like a serious limitation today, but in an era when most data was stored on magnetic tape such operations were too expensive to contemplate anyway.

Solutions were found to many of these problems.

Prime Computer created a CODASYL compliant DBMS based entirely on B-Trees that circumvented the record by record problem by providing alternate access paths.

They also added a query language that was very straightforward.

Further, there is no reason that relational normalization concepts cannot be applied to CODASYL databases however, in the final tally, CODASYL was very complex and required significant training and effort to produce useful applications.