Experimental Physics and
Industrial Control System

Andrew Johnson <[email protected]> · Fri, 8 Jan 2016 10:18:26 -0600

To complete the documentation around this topic:

There are some some cases/people/projects/sites that want to flag
loading duplicate records as an error. For them, there is a control
variable that can be set to make dbLoadRecords() print an error message
if a record already exists with the same name (available in all Base
releases back to 3.14.8). From the iocsh the command to set that is
    var dbRecordsOnceOnly 1
or from the VxWorks shell
    dbRecordsOnceOnly=1

- Andrew

On 01/08/2016 08:18 AM, Kasemir, Kay wrote:
> Hi:
> 
> Loading several *.db files can be a very useful approach.
> Typically you first load *.db files that define all the records, then later load additional *.db files which add fields to those records.
> Loading more *.db files that modify fields that were already defined can be a bit confusing to maintain in the long run, but adding fields is often a good idea.
> For example, the original *.db files can define the logic, and later you load *.db files that set ASG.
> For this to “work”, the record type must remain the same, unless you have a very new release of EPICS base.
> From the 3.15.0.2 release notes:
> ------
> Database field setting updates
> 
> A database (.db) file loaded by an IOC does not have to repeat the record type of a record that has already been loaded. It may replace the first parameter of the record(type, name) statement with an asterisk character inside double-quotes, "*" instead. Thus the following is a legal database file:
> 
> record(ao, "ao1") {}
> record("*", "ao1") {
>     field(VAL, 10)
> }
> ------
> 
> 
> The “*” for a type was specifically supported to allow
> 
> record(ao, “some_record)
> {
>   logic-related fields ..
> }
> 
> Then another *.db file:
> 
> # Don’t care about the record type, just want to configure access security:
> record(“*", “some_record)
> {
>   field(ASG, “SPECIAL”)
> }
> 
> -Kay
> 
>>> On Fri, Jan 8, 2016 at 7:40 AM, <[email protected]> wrote:
>>> I have implemented a record in two separate files which I then use substitutions to combine into a single db file. I am unsure I am allowed to do this after talking to a colleague; he is worried that this will create 2 PVs with identical names. My DB file contains (after make):
>>>
>>>
>>> record(ai, "NAME") {
>>>   field(DESC, "A PV")
>>>   field(EGU, "Gauss")
>>> }
>>>
>>> ...
>>>
>>> record(ai, "NAME") {
>>>   field(FLNK, "ANOTHER_RECORD")
>>> }
>>>
>>> Does this do what I am expecting, which is to create a single PV:
>>>
>>>
>>> record(ai, "NAME") {
>>>   field(DESC, "A PV")
>>>   field(EGU, "Gauss")
>>>   field(FLNK, "ANOTHER_RECORD")
>>> }
>>>
>>> Thank you.
>>>
>>> John
> 
> 

-- 
There are only two hard problems in distributed systems: 2. Exactly-once
delivery 1. Guaranteed order of messages 2. Exactly-once delivery
 -- Mathias Verraes

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System