How to increase the retention time of System performance statistics

Hello All,

We are troubleshooting performance issues in SAP Portal. Checking for response times and other statistics inside NWA ->Availability and Performance->System Performance Statistics.

Here we get only the current time data. Need help in the following

1. Is there anything needs to be changed if need the stats for say last 24hrs.

2. If I give give the start time spanning say 1 hour get the error as Maximum number of records exceeded.

Any help in this regard is appreciated.

Thanks

Uday