I m using ERWIN to generate SQL script for Oracle,
Can i do the same thing with Postgresql?

With the correct data type.
like VARCHAR2(n) -> character varying(n).

You can always generate the database script through ERWIN and if anything is not right, you can always edit it, then execute the script. I worked with Oracle a long time and see very litle difference between it and other SQL-compliant rdms'. The basics are the same. Oracle just has beter performance, is more reliable, supports more concurrent users, and has a more sophisticated back-up and recovery system and data wharehousing capability than free databases. I'm positive you can forward engineer your Oracle database schema to postgreSQL or MySQL.

Did you check this link out?

http://www.postgresql.org/docs/curre...l-porting.html

If you are only dealing with datastructures then you can port the schema quite easily with some editing. Know the data types of both databases however. You can really screw things up if you don't.