Re: Question related to PV record

["Kasemir, Kay" <kasemirk@ornl.gov>]

Hello:

>I am facing the problem that if the link is broken or not connected then the last stored values are being displayed in IOC by putting caget and caput commands. >How can i resolve this ? Is there any procedure to clear the last stored value ?

As Mark mentioned, EPICS records are by design keeping the last value.
They don't "clear" it. For one, what would "clear" mean? Set the value to zero? What if zero could also be a valid value? Set the value to NaN? Can't do that with longin, bi, mbbi, mbbiDirect, .. records.
Also, to debug a problem it can be helpful to know the last value we received before experiencing a read error.
Instead, records tend to keep the last known value and add for example a READ alarm with INVALID severity in case of read errors.
Strictly speaking it's not the record but device support which sets the value of the record, so one could implement device support that sets the value to "-1" or "0" or "NaN" in case of errors, but as far as I know most leave the value untouched in case of errors.

Most GUI tools would reflect the alarm state: You see the last known value, but there's for example a purple border around the widget to indicate that we don't really know the current value, it has an INVALID alarm severity.

The 'caget' command will by default not show alarm detail, but when you use 'camonitor' you'll see the alarm.
With 'caget', check 'caget -h' for the various request type options.
Given a numeric record,
   caget -d DBR_STS_DOUBLE YourPVName
will show the value with alarm status & severity.

-Kay