Wondering which component of database is in use?

DBA_FEATURE_USAGE_STATISTICS - Displays database feature usage statistics.

SELECT u1.name,

       u1.detected_usages

FROM   dba_feature_usage_statistics u1

WHERE  u1.version = (SELECT MAX(u2.version)

                     FROM   dba_feature_usage_statistics u2

                     WHERE  u2.name = u1.name)

ORDER BY u1.name;

DBA_HIGH_WATER_MARK_STATISTICS - Displays high watermark statistics.

SELECT hwm1.name,

       hwm1.highwater,

       hwm1.last_value

FROM   dba_high_water_mark_statistics hwm1

WHERE  hwm1.version = (SELECT MAX(hwm2.version)

                       FROM   dba_high_water_mark_statistics hwm2

                       WHERE  hwm2.name = hwm1.name)

ORDER BY hwm1.name;

You may also use this through OEM(Administration->Database Feature Usage).

HTH:-)