how to tune the performance of following query?

[sapen]

Hello,.

I am using the following query :

SELECT v~vbeln vgbel aubel vbtyp into corresponding fields of table gt_vbrp
FROM vbrp as v inner join vbrk on v~vbeln = vbrk~vbeln FOR ALL ENTRIES IN gt_ekko
WHERE aubel = gt_ekko-ebeln AND v~VBELN IN BILLNO.

BILLNO is a Select option variable.

Regards.