Modifying Non-SQL Defined Databases › Changes to Schemas and Subschemas › Methods for Modifying

Methods for Modifying

Depending on the type of change you want to make to a non-SQL defined database, you would do one of the following:

• Change the definition
• Change the definition and additionally use one or more utility statements

Basic Definition Change

To change a logical database definition when there is no impact on data, you can use the schema compiler (or another compiler). This type of change takes effect without requiring the use of a utility statement.

An example of a change in which there is no data impact is adding a new area to a schema.

Definition Change Using Utility Statements

For database changes that have an impact on data, you must change the database definition and additionally use an appropriate utility statement:

• RESTRUCTURE—Modifies record occurrences to fit new schema specifications. RESTRUCTURE allows you to:
  • Insert new data items anywhere in a record
  • Delete existing data items
  • Change the length and position of data items
  • Change the format of a record from fixed length to variable length or from variable length to fixed length
  • Add or remove record compression
  • Delete chained sets and add or delete set pointers
• REORG and UNLOAD/RELOAD—Reorganizes data when changes are made to the placement of records and indexes within the database (for example, moving a record from one area to another).
• MAINTAIN INDEX—Builds, rebuilds, or deletes indexes in the database. You use this utility whenever you need to make a structural change to the database involving indexes (for example, adding a new index to the database).