Few differences between Global Temporary Table and Volatile Table

 Global Temporary tables (GTT) :

• Table Definition is stored  into Data Dictionary.
• Data is stored in temp space.
• GTT data is active upto the session ends, but table definition will remain there in Data dictionaly untill is is dropped  using Droptable statement.
• secondry Index can be created on Global Temporary table.
• Stats can be collected on GTT.
• CHECK or BETWEEN constraints, COMPRESS column and DEFAULT and TITLE clause are supported by Global Temporary table.
• In a single session 2000 Global temporary table can be materialized.

Volatile Temporary tables (VTT) :

• Table Definition is stored in System cache.
• Data is stored in spool space.
• VTT data and table definition both are active only upto session ends.
• secondry Index can not be created on Global Temporary table.
• stats cannot be collected on VTT.
• CHECK or BETWEEN constraints, COMPRESS column and DEFAULT and TITLE clause are not supported by GTT.
• In a single session 1000 Volatile temporary table can be materialized.
• VTT does not support default value for a column while creating a table.