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Don Burleson Blog 







Multi-tenant local vs. common users tips

Oracle Database Tips by Donald BurlesonMarch 6,  2016

Question: In Oracle 12c, I see that users must start with a double pound sign, like ##c

What do I do when my instance looks up due to the log archive destination getting full?  I see this message, indicating that the directory is full:

Answer:  Oracle 12c has started making the multi-tenant the default behavior, and Oracle makes a distinction in multitenant databases for local vs. "common" user ID's:

  • COMMON USERS:  Common user ID's must always be created at the CDB level and start with a C## or c## prefixes. Oracle does not recommend that common users be used as schema owners.

  •  LOCAL USERS:  Local users can only be created at the PDB layer; also must use the CONTAINER clause set to CURRENT for the user to be created.
When creating a local (pdb) user, we must use the "container" clause.  Here, we move from the container database to the pdb database (using the "alter session set container" clause), and then create a pdb user:

alter session set container=my_pdb_name;

create user fred identified by flintstone container=current;

Local users differ from common users in these respects:

- Local user ID's cannot create user ID's or grant privileges.

- Local user ID's can grant local user accounts common roles.

- Local user ID's  must be unique within the PDB.

- Local user ID's can be granted access to a common user's schema.

- Local user ID's can be editions-enabled.

Common user ID's are created with the "container=all' syntax, and a container user ID should not be used to create schema tables.  Also, only common users are capable of navigating between PDB's.

Also, see my notes on creating common users without the c##_prefix. 

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