performance issue for VL01N transaction

Hi,

When the user opens the VL01N transaction and enters the corresponding mandatory fields and if he press enter for going to,

Next screen it is geting problem, The problem is if single user opens that transaction it is taking 10-minutes to move to next

screen .If multiple users opens that transaction ,at this time it is moveing first screen to second screen with in seconds.

Can any one help me how to resolve this problem.

Thanks & Regards,

Anvesh Gummadapu.