The "O7_DICTIONARY_ACCESSIBILITY" setting is a database initializations parameter that allows/disallows with the EXECUTE ANY PROCEDURE and SELECT ANY TABLE access to objects in the SYS schema; this functionality was created for the ease of migration from Oracle 7 databases to later versions.
As leaving the SYS schema so open to connection could permit unauthorized access to critical data structures, this value should be set according to the needs of the organization.
Eventually, if this parameter is set to TRUE without your knowledge, your database may be at risk.
From Oracle Docs:
For example, if "O7_DICTIONARY_ACCESSIBILITY" is set to false, then the SELECT ANY TABLE privilege allows access to views or tables in any schema except the SYS schema (data dictionary tables cannot be accessed). The system privilege EXECUTE ANY PROCEDURE allows access on the procedures in any schema except the SYS schema.
If this parameter is set to false and you need to access objects in the SYS schema, then you must be granted explicit object privileges. The following roles, which can be granted to the database administrator, also allow access to dictionary objects:
As leaving the SYS schema so open to connection could permit unauthorized access to critical data structures, this value should be set according to the needs of the organization.
Eventually, if this parameter is set to TRUE without your knowledge, your database may be at risk.
From Oracle Docs:
For example, if "O7_DICTIONARY_ACCESSIBILITY" is set to false, then the SELECT ANY TABLE privilege allows access to views or tables in any schema except the SYS schema (data dictionary tables cannot be accessed). The system privilege EXECUTE ANY PROCEDURE allows access on the procedures in any schema except the SYS schema.
If this parameter is set to false and you need to access objects in the SYS schema, then you must be granted explicit object privileges. The following roles, which can be granted to the database administrator, also allow access to dictionary objects:
- SELECT_CATALOG_ROLE
- EXECUTE_CATALOG_ROLE
- DELETE_CATALOG_ROLE
