PostgreSQL to Oracle8i conversion problem

[Ingrid]

Hi,
I'm working on a JDBC application that issues an sql command to
a PostgreSql database that fetches only a certain amount of rows
at a time :

sql.append(" limit ").append(num).append(",").append(start);

variables are :
num = # of rows to be returned from the sql SELECT statement
start = row from where to start

if I place
...WHERE ROWNUM <= 100 and then
something ...WHERE ROWNUM > 100 returns nothing (?!)

Can someone give me a hint on how to do this with 8i ?

Also PostgreSQL has the boolean column type.
What should I used for the otacle vcersion ?

Thanx in advance.