I think of physical and logical this way:
Physical = what files you actually see on the server and operating
system. You see a datafile located at c:\location\db\users.dbf
That is a physical file. When you make a physical backup this file is being copied or backed up.
Logical = anything that you only see once you login to the database. You select data from a table.
That data is STORED in a physical datafile but can only be viewed from inside the database (logically).
A "tablespace" needs a datafile assigned to it. You do not SEE the tablespace from the server/OS
level but you CAN see the datafile. A logical backup would be a backup of all the DATA in a database.
You could only recover the data by recreating a new database and importing that logical
data (tables, rows, indexes, etc).
A tablespace can have many physical datafiles assigned to it.
So, maybe 3 datafiles of a size of 2G are assigned the USERS tablespace.
This would give the USERS tablespace a size of 6G.
In the old days of technology servers were sometimes limited to a maximum file size.
So, by assigning 50 datafiles of 2G each Oracle could then have a tablespace with a size of 100G
while the operating system thinks that all it has are 2G files which stay below the maximum size allowed.
(hopefully I didn't fuck any of this information up)
Last edited by The_Duck; 10-28-08 at 18:39.
you can lead someone to something but they will never learn anything ...