Record (File architecture): Difference between revisions
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== The Concept of a Model 204 Record == | == The Concept of a Model 204 Record == | ||
=== Base Records === | === <div id="Base Records">Base Records</div> === | ||
=== Extension Records === | === Extension Records === | ||
=== The Internal Record Number (IRN) === | === <div id="Internal Record Number">The Internal Record Number (IRN)</div> === | ||
not permanent (changes during a reorganization) | not permanent (changes during a reorganization) | ||
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== The Structure of a Model 204 Record == | == The Structure of a Model 204 Record == | ||
::[[File:Record Structure (File Architecture).jpg]] | |||
=== Extension Pointer === | === Extension Pointer === | ||
Revision as of 23:46, 10 April 2013
A Model 204 Record is a collection of fields (either individually or in Repeating Field Groups (RFGs)).
Each record is variable in length and need contain only the fields that pertain to it. The limit of the number of field value pairs in a record is in the tens of millions.
There is only a limited fixed format for a record (pre-allocated fields). Almost any number of fields can appear almost any number of times in almost any order. Each record is automatically assigned a unique internal record number that is used by the system to build index entries for the record.
The Concept of a Model 204 Record
Base Records
Extension Records
The Internal Record Number (IRN)
not permanent (changes during a reorganization)
used as target index (both hashed and B-tree indexing)
The Structure of a Model 204 Record
.jpg)
Extension Pointer
Data
If there are any preallocated fields in a file (see the OCCURS attribute) every record in that file will begin with the set of such fields. The set of fields is stored in the Record Map in Table D.
After that, in either the order they were ADDed (which always adds the entity at the end of the record), or positioned by an INSERT statement, come a series of field value pairs, repeating field groups and / or pointers to large objects.
Each of the four is described below: