Temporary Table spaces
A temporary table space contains transient data that persists only for the duration of a session. No permanent schema objects can reside in a temporary table space. The database stores temporary table space data in temp files. Temporary table spaces can improve the concurrency of multiple sort operations that do not fit in memory. These table spaces also improve the efficiency of space management operations during sorts.
When the SYSTEM table space is locally managed, a default temporary table space is included in the database by default during database creation. A locally managed SYSTEM table space cannot serve as default temporary storage. You can specify a user-named default temporary table space when you create a database by using the DEFAULT TEMPORARY TABLE SPACE extension to the CREATE DATABASE statement. If SYSTEM is dictionary managed, and if a default temporary table space is not defined at database creation, then SYSTEM is the default temporary storage. However, the database writes a warning in the alert log saying that a default temporary table space is recommended.
Duration of an Instance
An instance begins when it is created with the STARTUP command and ends when it is terminated. During this period, an instance can associate itself with one and only one database. Furthermore, the instance can mount a database only once, close it only once, and open it only once. After a database has been closed or shut down, you must start a different instance to mount and open this database.