SLOW datafile read problem

I've got stored procedure that performs about 200 DML operations. In half a way Oracle dramaticly slows down. The session waits for:

db file scattered read or db file sequential read

I tries to read 7 blocks of data from the only one file in tablespace that is 200MB long.
It waits obout 400 seconds (!!!) and then ... tries to read the same file but BLOCK#
is increased by 7. I am using

Oracle7 Server Release 7.3.4.0.0 - Production PL/SQL Release 2.3.4.0.0 - Production
CORE Version 3.5.4.0.0 - Production
TNS for 32-bit Windows: Version 2.3.4.0.0 - Production NLSRTL Version 3.2.4.0.0 - Production

on 1 processor sever Pentium II 300MHz with 128MB

WHAT SHOULD I DO TO SPEED UP THE PROCEDURE EXECUTION ??? Thanks in advance

                                        Martin