>>It looked as if FB does not use cache data. What to set?

>>select sum(price) from inv_rows, inv_heads, companies
>>where inv_rows.invcode=inv_heads.invcode and
>>inv_heads.compid=companies.compid and
>>companies.compname like 'A%'

Thanks,
I tested your example but the time is the same.
I tested also index "starts with", the time is better (i forgot that "like"
does not use indexes).
My problem, why first query has the same access time as next queries,
continues.

Can I get some informations HOW many of buffers are _REALLY_ used by server
and WHAT contain?

Best regards,
Leos