Remote plan hints
Plan hints are statement fragments that provide extra information to data source optimizers.
Use the PLAN_HINTS server option to generate remote plan hints. This information can, for certain query types, improve query performance. The plan hints can help the data source optimizer decide whether to use an index, which index to use, or which table join sequence to use.
You should run some tests to determine if this server option will improve the performance of your queries.
You cannot code your own plan hints in a query.
If plan hints are enabled, the query sent to the data source contains additional information. For example, a statement sent to an Oracle optimizer with plan hints could look like this:
SELECT /*+ INDEX (table1, tlindex)*/ col1 FROM table1
The plan hint is the string /*+ INDEX (table1, t1index)*/