It might be in use by the report. Check the data session for the report.
Also try this...
IF NOT USED('myDumbTable')
USE myDumbTable EXCLU IN 0
ENDIF
ZAP IN myDumbTable

This assumes that if previously opened it was opened exclusive. If not always the case then...

IF USED('myDumbTable')
SELECT myDumbTable
ELSE
SELECT 0
ENDIF
USE myDumbTable EXCLU
ZAP IN myDumbTable

>Hi,
> I have a table. I use it as my temporary table to store the result of last report generated. After my times of report generated, the dumb data in this table become bigger and bigger. Therefore, I provide ZAP function to client. I don't include the table in my form's dataenvironment. I issue
>
>

>USE myDumbTAble EXCLUSIVE
>ZAP
>
>SELECT * FROM ..... && my next operation
>
>

>
>I got File is in use error. It only work fine once I issue close table all in command window. I try to issue
>
>CLOSE TABLE ALL or
>
>SELECT mydumbtable
>USE
>
>but it doesn't work. why?
>
>Thank you