File sharing, locking, etc... between multiple users...

[Jim Ault]

On 2/18/06 6:39 AM, "Kurt Kaufman" <kkaufman at snet.net> wrote:

> Is this how most databases function?
> 
>> On further thought on the record locking..
>> It might be possible for you to take the approach that the real
>> field is
>> never edited real time, but only a temp field that is later
>> processed in the
>> time sequence (the seconds) 'submitted' in an orderly event loop.
>> This way,
>> 4 users could be editing the "same field" while seeing that other
>> users are
>> doing likewise ("chat room style").

Not usually.
The 'locking' refers to a user connecting to a database and not allowing any
other editing of the record (record-locking) or field (field-locking) until
that user releases control.
Thus, only one edit at a time.  Imagine two ticketing agents for an airline
selling the last first class seat for a flight in few weeks to different
people, one agent in New York, another in Paris.  Record locking prevents
this.

Another dilemma would be if a third person asked the database for the value
of a field that was in the process of being edited... What value do you
report to that third person?

Then add to that, a field that was allowed to be edited by two different
users, neither of which was done with the edit.  Which version is correct?
Which version replaces the other two?

Fun and games.

Jim Ault
Las Vegas