Useful tables for database management and patches

When you wonder where a column or code is used you can use the following query!

select * from all_source
where upper(TEXT) like '%%',

Also a few useful tables are listed below:

-dba_db_links
-dba_tables
-v$database

Useful tables for patch information whether it is installed or not:
ad_bugs, ad_applied_patches

From ETRM:
"AD_BUGS holds information about the various Oracle Applications bugs whose fixes have been applied (ie. patched) in the Oracle Applications installation

AD_APPLIED_PATCHES holds information about the "distinct" Oracle Applications patches that have been applied. If 2 patches happen to have the same name but are different in content (eg. "merged" patches), then they are considered distinct and this table will therefore hold 2 records."