DDIC is a data dictionary user which can access all SAP objects without any restriction.
Support patch will have many corrections/changes on standard objects and it doesn't require any Go/No go confirmation. DDIC never ask for any confirmation from user end while update/upgrade/changes, you should use equallent Id instead of DDIC for this purpose.
*SAP* should not be used for any purpose (Updates/Upgrades/Changes etc.) other than for logins until unless you have user master record!
Search Google/SDN with a key word "DDIC in 000".
Read and follow RoE.
Regards,
Nick Loy