Performance of Select Query on BSEG

Hi,

I'm trying to develop a report which involves BSEG, BKPF etc. tables and this BSEG contains around 30Cr records and BKPF contains 5Cr records (It is even leading to a timeout error when I'm trying to see the no of entries in BSEG table). I'm doing a SELECT on BKPF first, passing BUKRS and GJAHR and then based on the records fetched from BKPF, I'm doing another SELECT on BSEG passing BUKRS, BELNR and GJAHR. It is giving a timeout error after 30 minute. Please suggest a better way for this.

Thanks in advance.

Regards,

Pritam