Rowid in Oracle 8i

Dear Friends,

I m new to this form, if i did anything wrong please forgive me.

Recently i faced a problem regarding Rowid values in Oracle 8i. I want some more information regarding Rowids.
My queries are
1) Is it possible to change the Rowid values in the datebase.(by using queries like that)
2) Is there any way automatic Jump of rowids in database.

Actually rowid values increment by 1 .but recently rowid value is jumped to another value (Unexpected value) automatically in my database, I want to know how it is possible?

Thanks in advance..

Regards,
hlp4al