Experimental Physics and
Industrial Control System

Marty Kraimer <[email protected]> · Tue, 03 Feb 1998 13:34:20 -0600

Let me summarize the situation:

There are at least two ways to allow CA clients to retrieve the record
type and a version identifier for a record type/record support
combination:

1) Add two new fields RTYP and VERS
2) Add two new DBR_types

Here are arguments for/against each

New fields RTYP and VERS

Argument for:

Existing CA clients automatically have access to new info.

Arguments against:

1) Each record instance will use extra storage for new fields.
2) Not elegent, i.e. info is associated with record instances that
belongs to record type.
3) A CA client that wants to provide a builtin capability to get record
type/version must know how to strip field name from channel name and
then add .RTYP or .VERS

New DBR_types: Arguments for/against are the reverse of those for new
fields.

I am starting to think that allowing existing CA clients to work without
change is more important than the other arguments.

For Channel Access Version 4 and database Access version 4 we should
solve these problems in a much nicer way but maybe for version 3 adding
new fields is best.

Marty Kraimer

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System