index usage monitoring / invisible indexes

In an application lifecycle some indexes will be added to a table, again and again.

But after a while nobody knows which index is really used or not.

Just delete the index ? hmmm who knows 😉

A simple option is to use index monitoring.

alter index <index_name> monitoring usage;

online rebuild index fails ora-8104

When you kill a session which is rebuilding an index this will cause an ora-8104.
SQL> ALTER INDEX I_TEST  REBUILD ONLINE ;
ALTER INDEX I_TEST  REBUILD ONLINE
*
ERROR at line 1:
ORA-08104: this index object 11040 is being online built or rebuilt

Solution: