Modifying Schema Entities › Index Modifications › Changing Index Characteristics

Changing Index Characteristics

Types of changes

You can change the following index-related characteristics:

• Key compression
• Number of entries in an SR8 record
• Index displacement
• Index key or collating sequence

What components are affected

The schema set definitions and data are affected. Subschema and access modules that reference the member record are also affected.

Steps to change index characteristics

To change index characteristics when data has been loaded:

1. Add a new schema based on the original schema modifying the set characteristics
2. Validate the schema
3. Create a global subschema
4. Rebuild the index using the MAINTAIN INDEX utility and the REBUILD option
5. Complete the process by updating the original schema, regenerating affected subschemas, and altering affected access modules

Considerations

• If you change the index key, the control length of the member record may change. If it does, and the member record is compressed or variable in length, you must use RESTRUCTURE to change the control length of existing record occurrences.
• When you execute the MAINTAIN INDEX utility statement, use the REBUILD option:
  • If you change key compression, you must specify the name of an old subschema in the USING parameter and the name of a new subschema in the NEW SUBSCHEMA parameter.
  • If you change the symbolic key or the collating sequence, you must specify the new subschema in the USING parameter.

  If both types of change are being made at once, you will need to run MAINTAIN INDEX twice, once to delete the existing index (using the old subschema) and once to build the new index (using the new subschema).