Experimental Physics and
Industrial Control System

Maren Purves <[email protected]> · Mon, 02 Feb 2009 12:18:34 -1000

Benjamin Franksen wrote:

On Montag, 2. Februar 2009, Till Straumann wrote:

Benjamin Franksen wrote:

Our idea for an efficient implementation is based on the observation
that in a typical EPICS database there are only very few fields per
record that actually receive dbPuts (or get updated directly from
within base). Only for these fields is it necessary to provide storage
for the time of the last update. This storage will be allocated on
demand; each record must maintain a (typically very short) list of
(field index, timestamp) pairs; let us call it the 'field update list'
or short 'update list'. When reading the timestamp for a field, first
search the update list and use the contained stamp if one is found,
otherwise use the TIME field of the record.

How does that implement (b) ? If a field is never updated,
shouldn't that field then report the time when iocInit() was
executed?

Ah, a good objection. It looks as if we need to distinguish between fields

that have

 i)   never been changed (timestamp = iocInit time)

only if PINI=Yes?

 ii)  last been updated by record support (timestamp = record's TIME field)
 iii) last been updated via dbPut or from base (timestamp = see update list)

?

Maren

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System