Pre-condition to using Function Based Index

• init.ora

QUERY_REWRITE_INTEGRITY=TRUSTED
QUERY_REWRITE_ENABLED=TRUE
COMPATIBLE >  8.1.0.0.0

• privilege

CREATE INDEX /QUERY REWRITE /CREATE ANY INDEX
GLOBAL QUERY REWRITE.

• CBO (Cost Based Optimizer)

 Create statistics information by using analyze or use the index by using hint.

• RBO (Rule Based Optimizer)

 Function based index cannot be used in RBO. If the optimizer mode is Choose, the table should be analyzed.