Re: Can I override record definition twice in an IOC

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

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, <John.Holt@tessella.com> 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