Segments are the physical representation of the logical database objects. A segment is thus a subunit of a tablespace, and will be contained in a datafile. extents are subunits of a segment, and are defined as contiguous sets of Oracle blocks. Successive extents are not guaranteed to be contiguous, but within each extent the Oracle blocks are contiguous. A block is the unit of data that can be read or written to an Oracle data file, and is managed using PCT_FREE and PCT_USED, among others.
[QUOTE][i]Originally posted by m_d_marian [/i]
there are only one segment for an object.
Not necessarily so. A table (object) can have partitions (subobjects), and partitions are segments. So with partitioned tables and indexes you have more than one segment for table/index.
That means than an segment can be spread on multiple files? [/B][/QUOTE]
Jurij Modic ASCII a stupid question, get a stupid ANSI
24 hours in a day .... 24 beer in a case .... coincidence?