In Oracle, how can I give one user privileges to alter the schema of another user? I have an Oracle DB (10.2), and I have a consultant (Dogbert) that I want to do some work on it. In particular they need to alter the table structures of tables in a schema (we'll call it Wally) that is used by a lot of my users.

I don't want to give Dogbert the password to the account to the Wally schema. So I've created a temporary account for Dogbert. 

How can I give Dogbert's account permission to alter the structure of Wally's schema? I know I can certainly give Dogbert insert/update/delete/select but that doesn't affect the structure.
You can use CONNECT THROUGH to allow Dogbert to connect as Wally:

alter user wally grant connect through dogbert;
grant create session to dogbert;


To connect in sqlplus:

sqlplus dogbert[wally]/scottadams@DATABASE


Some tools may not support these proxy logins.