It looks like an illegal command to me.
OXCA is the same as 202, _ERR is probably an error number. So !_ERR=0XCA is a comparison reporting either .T. or .F. This means that the whole expression FLUSH !_ERR=0XCA will translate into FLUSH .T. or FLUSH .F., but both of these commands are illegal.

>In an inherited application I found the following FLUSH command.
>
>FLUSH !_ERR=0XCA
>
>Anyone know what the !_ERR=0XCA is?
>
>
>Harry