$ORACLE_HOME/OPatch/datapatch

datapatch is typically used to patch data «within» a database and needs therefore to be run while the database is running.

This is in contrast to opatch which is typically used to patch files located in the Oracle Home (such as Oracle binaries or timezone files).

See also Contents of a patch file

The real work of datapatch is actually performed by $ORACLE_HOME/sqlpatch/sqlpatch.