> i saw field(SCAN, "I/O Intr") in record .. .
> what is mean?
The original meaning of "I/O Intr" was to scan the record on an _interrupt_ from the I/O device, for example some ADC card that can generate an interrupt.
Technically is just means that some EPICS device support modules can process the record when they decide that it's a good time to process the record, for example because the underlying hardware or network protocol provided a new value.
The stream device supports this as shown in the manual under
. It typically requires one record to send a command to the device, and from then on the device will on its own send updates. As the stream device receives text from the device, it
will then process records that are configured to with SCAN=I/O Intr.