Aarthi,
if the script ws running correctly and response Time(RT) 
was 2.5 secs tht time. After a fix RT increased to 5 secs. 
then wt i sugguest you to run d same script with a goal 
oriented scenario. keep same no. of Vusers and rest of the 
settings. limits the RT to 2.5 secs max. During running of 
d you'll get the msg tht limit is about to exceed. for this 
wht you do tht u instruct d controller to continue scenario 
execution if the limits exceed in scenario configuration. 
Now run the scenario, and monitor tht at what point during 
the script execution RT exceeded d limits. U'll b able to 
get the exact answer of ur problem. u'll b able to knw tht 
is d prblm in app server or database server?

Satisfied ot not?
plz respond

Thnks
rohit