Top Daily Used Oracle Hints for Performance Tuning and Query Optimization

Top Daily Used Oracle Hints for Performance Tuning and Query Optimization

HINTS MEANINGS	Description
[NO]APPEND	This specifies that data is to be or not to be appended to the end of a file rather than into existing free space. Use only with INSERT commands.
[NO]APPEND	For insert operations will append (or not append) data at the HWM of table.
ACCESS METHODS ORACLE HINTS
ALL_ROWS	Use the cost based approach for best throughput.
AND_EQUAL(table index index [index index index])	This hint causes a merge on several single column indexes. Two must be specified, five can be.
CACHE	Specifies that the blocks retrieved for the table in the hint are placed at the most recently used end of the LRU list when the table is full table scanned.
CHOOSE	Default, if statistics are available will use cost, if not, rule.
CLUSTER(table)	This tells Oracle to do a cluster scan to access the table.
FACT(table)	When performing a star transformation use the specified table as a fact table.
FIRST_ROWS	Use the cost based approach for best response time.
FULL(table)	This tells the optimizer to do a full scan of the specified table.
HASH(table)	Tells Oracle to explicitly choose the hash access method for the table.
HASH_AJ(table)	Transforms a NOT IN subquery to a hash anti-join.
HASH_SJ(t1, t2)	Inserted into the EXISTS subquery; This converts the subquery into a special type of hash join between t1 and t2 that preserves the semantics of the subquery. That is, even if there is more than one matching row in t2 for a row in t1, the row in t1 is returned only once.
INDEX(table [index])	Forces an index scan of the specified table using the specified index(s). If a list of indexes is specified, the optimizer chooses the one with the lowest cost. If no index is specified then the optimizer chooses the available index for the table with the lowest cost.
INDEX_ASC (table [index])	Same as INDEX only performs an ascending search of the index chosen, this is functionally identical to the INDEX statement.
INDEX_COMBINE(table index)	Combines the bitmapped indexes on the table if the cost shows that to do so would give better performance.
INDEX_DESC(table [index])	Same as INDEX except performs a descending search. If more than one table is accessed, this is ignored.
INDEX_FFS(table index)	Perform a fast full index scan rather than a table scan.
LEADING(table)	The hint causes Oracle to use the specified table as the first table in the join order.
MERGE_AJ (table)	Transforms a NOT IN subquery into a merge anti-join.
MERGE_SJ (t1, t2)	Inserted into the EXISTS subquery; This converts the subquery into a special type of merge join between t1 and t2 that preserves the semantics of the subquery. That is, even if there is more than one matching row in t2 for a row in t1, the row in t1 is returned only once.
NL_AJ	Transforms a NOT IN subquery into a NL anti-join (nested loop).
NL_SJ	Inserted into the EXISTS subquery; This converts the subquery into a special type of nested loop join between t1 and t2 that preserves the semantics of the subquery. That is, even if there is more than one matching row in t2 for a row in t1, the row in t1 is returned only once.
NO_EXPAND	Prevents OR and IN processing expansion.
NO_FACT(table)	When performing a star transformation do not use the specified table as a fact table.
NO_MERGE (table)	This causes Oracle to join each specified table with another row source without a sort-merge join.
NO_UNNEST	Turns off the UNNEST_SUBQUERY option for statement if UNNEST_SUBQUERY parameter is set to TRUE.
NOCACHE	Specifies that the blocks retrieved for the table in the hint are placed at the least recently used end of the LRU list when the table is full table scanned.
NOPARALLEL (table	This specifies the operation is not to be done in parallel.
NOREWRITE	Turns off query rewrite for the statement, use it for when data returned must be concurrent and can't come from a materialized view.
ORACLE HINTS for PARALLEL OPERATIONS
ORDERED	This hint forces tables to be joined in the order specified. If you know table X has fewer rows, then ordering it first may speed execution in a join.
Other Oracle Hints?
PARALLEL(table, instances)	This specifies the operation is to be done in parallel.
PARALLEL_INDEX	Allows parallelization of a fast full index scan on any index.
PUSH_PRED	Pushes the join predicate into the view.
PUSH_SUBQ	This causes nonmerged subqueries to be evaluated at the earliest possible point in the execution plan.
REWRITE(mview)	If possible forces the query to use the specified materialized view, if no materialized view is specified, the system chooses what it calculates is the appropriate view.
ROWID(table)	Forces a rowid scan of the specified table.
RULE	Use rules based approach; this cancels any other hints specified for this statement.
SITE	The hint forces query execution to be done at a different site than that selected by Oracle. This hint can be used with either rule-based or cost-based optimization.
STAR	Forces the largest table to be joined last using a nested loops join on the index.
STAR_TRANSFORMATION	Makes the optimizer use the best plan in which a start transformation is used.
UNNEST	Turns on the UNNEST_SUBQUERY option for statement if UNNEST_SUBQUERY parameter is set to FALSE.
USE_CONCAT	Forces combined OR conditions and IN processing in the WHERE clause to be transformed into a compound query using the UNION ALL set operator.
USE_HASH (table)	This causes Oracle to join each specified table with another row source with a hash join.
USE_MERGE(table,[table, -])	This operation forces a sort-merge-join operation of the specified tables.
USE_NL(table)	This operation forces a nested loop using the specified table as the controlling table.