Siebel Installation Guide for Microsoft Windows: Servers, Mobile Web Clients, Tools > Guidelines for Configuring the RDBMS > Creating Oracle Database Objects >

Creating Temporary Oracle Tablespaces

All user temporary tablespace definitions should be modified from the default of SYSTEM to the name of the temporary tablespace; for example, TEMP or TEMP_TS. Otherwise, SORT operations interfere with Oracle dictionary management.

To find out which users are assigned to which temporary tablespaces, query the TEMPORARY_TABLESPACE column of DBA_USERS, and if any users are assigned to a tablespace other than the one allocated for temporary sort-type operations, correct the situation.