how force kernel to detach the scsi drive and rescan the devices

i have installed a scsi card when i first install debian and after that i have replaced the scsi card with the same type of scsci card now i am getting the following error in my syslog i think because of the scsi card chaged

Mar 17 00:10:23 localhost kernel: scsi0:0:6:0: Device is active,
> asserting ATN
> Mar 17 00:10:23 localhost kernel: Recovery code sleeping
> Mar 17 00:10:28 localhost kernel: Recovery code awake
> Mar 17 00:10:28 localhost kernel: Timer Expired
> Mar 17 00:10:28 localhost kernel: aic7xxx_abort returns 0x2003
> Mar 17 00:10:28 localhost kernel: scsi0:0:6:0: Attempting to queue a
> TARGET RESET message
> Mar 17 00:10:28 localhost kernel: CDB: 0xa 0x0 0x0 0xfc 0x0 0x0
> Mar 17 00:10:28 localhost kernel: aic7xxx_dev_reset returns 0x2003
> Mar 17 00:10:28 localhost kernel: Recovery SCB completes
> Mar 17 00:10:33 localhost kernel: scsi: device set offline - not
ready
> or command retry failed after bus reset: host 0 channel 0 id 6 lun 0
> Mar 17 00:10:33 loc alhost kernel: st 0: Error 10000 (sugg. bt 0x0,
> driver bt 0x0, host bt 0x1).

please help me how to fix this problem