Few Things

[Fiza15]

Hi Friends,
What it means you connect to an idle instance??
Is Segment name is same as the Table name that we create??
Say DBW0 has info to write on datafile and the table space is off line where is that info go then??
What it means we say Maxextents 500 (is it #of Maxextents tablespace can have)??
Thanks alot for your time...

[cguillaume]

To connect to an idle instance means that you are connected to an Instance/database/Server that is SHUTDOWN. So you need to STARTUP so the database is accessible.

A segment is any object that requires physical storage outside the data dictionary. So if you create a table, it is also considered a segment. Same is true for indexes.

DBWR will not write to a datafile when the tablespace is offline.

Maxextents on a TABLESPACE is the max # of extents (chunks of space) that any 1 segment is allowed to have in that particular tablespace. Your tablespace space is limited to the size of your datafiles.