Query below return:

A. all User Defined Functions and objects used by them accessible to the current user in Oracle database.

B. all User Defined Functions and objects used by them in Oracle database.

Query

A. All User Defined Functions and objects used by them accessible to the current user

select owner || '.' || name as function_name,
       referenced_owner || '.' || referenced_name as referenced_object,
       referenced_type
from sys.all_dependencies
where type = 'FUNCTION'
      and name = 'function_name' -- put your function name here
      --and referenced_owner = 'schema name'
      and referenced_owner not in ('ANONYMOUS','CTXSYS','DBSNMP','EXFSYS',
          'MDSYS', 'MGMT_VIEW','OLAPSYS','OWBSYS','ORDPLUGINS', 'ORDSYS',
          'SI_INFORMTN_SCHEMA','SYS','SYSMAN','SYSTEM', 'TSMSYS','WK_TEST',
          'WKPROXY','WMSYS','XDB','APEX_040000', 'APEX_PUBLIC_USER','DIP', 
          'FLOWS_30000','FLOWS_FILES','MDDATA', 'ORACLE_OCM', 'XS$NULL',
          'SPATIAL_CSW_ADMIN_USR', 'SPATIAL_WFS_ADMIN_USR', 'PUBLIC',
          'OUTLN', 'WKSYS',  'LBACSYS') 
order by referenced_object;

B. If you have privilege on dba_dependencies

select owner || '.' || name as function_name,
       referenced_owner || '.' || referenced_name as referenced_object,
       referenced_type
from sys.dba_dependencies
where type = 'FUNCTION'
      and name = 'function_name' -- put your function name here
      --and referenced_owner = 'schema name'
      and referenced_owner not in ('ANONYMOUS','CTXSYS','DBSNMP','EXFSYS',
          'MDSYS', 'MGMT_VIEW','OLAPSYS','OWBSYS','ORDPLUGINS', 'ORDSYS',
          'SI_INFORMTN_SCHEMA','SYS','SYSMAN','SYSTEM', 'TSMSYS','WK_TEST',
          'WKPROXY','WMSYS','XDB','APEX_040000', 'APEX_PUBLIC_USER','DIP', 
          'FLOWS_30000','FLOWS_FILES','MDDATA', 'ORACLE_OCM', 'XS$NULL',
          'SPATIAL_CSW_ADMIN_USR', 'SPATIAL_WFS_ADMIN_USR', 'PUBLIC',
          'OUTLN', 'WKSYS',  'LBACSYS') 
order by referenced_object;

Columns

• function_name - function name
• referenced_object - schema name and name of the referenced object
• referenced_type - type of referenced object

Rows

• One row represents one referenced object by provided function
• Scope of rows: all objects that are used by function in database
• Ordered by schema name and name of referenced object

Sample Result