Set identity_insert in Oracle

is there anything similar to the sql command
'set identity_insert <tblname> on' in ORACLE 9i.
my column in the table in oracle does not have any identity constraints defined on it but everytime i insert data it starts from the last value


for eg.. if i have 3 records starting with an id '3' upto 6 and i want to insert a record with id '1' then it doesn't take it and the record gets inserted with id 4 ........despite of the column not having any identity constraint on it................................

any suggestions will be grateful,

thanks

Radz