PROBLEM:

While assigning default tablespace for a user, got an ORA-12910 error.

SQL> alter user dba_raj default tablespace TEMP;
alter user dba_raj default tablespace TEMP
*
ERROR at line 1:
ORA-12910: cannot specify temporary tablespace as default tablespace

SOLUTION:

As the error says, we can’t set a temporary tablespace as default tablespace for a user. We can only set as a PERMANENT tablespace.
We can get the type of tablespace by using below query.

SQL> select tablespace_name,contents from dba_Tablespaces;

TABLESPACE_NAME                CONTENTS
------------------------------ ---------
SYSAUX                         PERMANENT
SYSTEM                         PERMANENT
TEMP                           TEMPORARY ---- ----  >>>>>> 
TEST                           PERMANENT
TEST_2                         PERMANENT
TS_CRM_EXTCH                   PERMANENT
TS_GGATE                       PERMANENT
USERS                          PERMANENT
UNDOTBS1                       UNDO

So just use a tablespace with PERMANENT type.

SQL> alter user dba_raj default tablespace TS_GGATE;

User altered.