Experimental Physics and
Industrial Control System

On Mar 7, 2021, at 12:09 AM, Wang, Andrew via Tech-talk <tech-talk at aps.anl.gov> wrote:

In the OUTLINK section of the documentation (https://epics.anl.gov/base/R3-16/1-docs/AppDevGuide/DatabaseLockingScanningAndProcessing.html#x6-2040005.12.2), it says that

It is not possible to honor PP or NPP options; the put operation completes immediately but whether the destination record will process depends on the process passive attribute of the destination field.

Could I get a clarification that? The reason why is because earlier in the Passive Process section, it says that

It determines if the linked record should be processed before getting a value from an input link or after writing a value to an output link.

From what is described in the second section, it appears that we can specify PP or NPP in the OUT field of a record. However, in the first portion, it appears to say otherwise.

Subsection 5.12.2 of the manual where it says PP & NPP aren’t available for OUTLINK types is part of section 5.12 Channel Access Links, so that comment only applies to CA links. If the link points to a record in another IOC (or if it points to a local record but also has a CA flag to force it to be a CA link) a PP or NPP flag won’t have any effect. CA links use the same network protocol and behave exactly like any other kind of CA client, so whether a put causes processing depends purely on the attribute of the field in the record type that the put is directed to.

HTH,

- Andrew