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ALTER INDEX Statement (alter_index_statement) 

The ALTER INDEX (alter_index_statement) statement determines how an index is used in data queries.

Syntax

<alter_index_statement> ::= ALTER INDEX <index_name> [ON <table_name>] ENABLE
| ALTER INDEX <index_name> [ON <table_name>] DISABLE
| ALTER INDEX <index_name> [ON <table_name>] INIT USAGE

index_name, table_name

Explanation

When a CREATE INDEX statement is executed, an index is generated across the specified columns. This index is modified accordingly for all of the following SQL statements for data manipulation (INSERT statement, UPDATE statement, DELETE statement). With all other SQL statements in which individual rows in a table are specified, the database system can use this index to speed up the search for these rows.

ALTER INDEX … DISABLE

The index can no longer be used for this search, however it continues to be changed by the use of the SQL statements INSERT, UPDATE, or DELETE.

ALTER INDEX … ENABLE

The index can be used for the search again.

ALTER INDEX … INIT USAGE

The column INDEX_USED in the system table DOMAIN.INDEXES is initialized with 0; that is, the count of how often an index is used is restarted.

 

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