Oracle database physical structure contains

1. Data files -- always occupy the declared size on the hard disk irrespective of the rows contained in them (.dbf). The data files contain
• Data blocks -- smallest unit of I/O. each block contains a header
• ROWID -- two byte pseudo column to identify phsical location of a row
• Table clusters -- tables which are often used together in queries are physically grouped in same data block. Cluster tables are joined on 'cluster key' which identifies the common column between the two tables.
2. Online redo log files (.rdo and .arc)
3. Control files -- contain one slot per data file declared for a database. Also contain other configuration parameters. (.ctl)
4. Password files.
5. sidALTR.log files -- log critical failures
6. Trace files -- saves user session traces (.trc)

Physical database components are : Database files control files & Redo log files.

Database files : Contains actual data & which is very largre files.

Control files : contains inforrmation regarding database files & it records the changes makes to database files.

Redolog files : When every changes makes to databases it records into Redolog files .

physical structures consist of three core database files

1> datafile... used to store the actual data in the database.

2> redologfile.. stores all changes which are to made in the database. oracle

keeps two redolog files in the db. in separate disk so that during disk failure

we can recover the database.

3> controlfile.. which stores the physical location of the datafile stores the scn for each and every update in datafile and redolog file.. we can also recover the database from control file also....