Hi.  Using DBISAM Version 4.24 Build #1.  Due to the nature of my
application and how some of the automation features operate, I need to use
Optimistic record locking.

However, there are some areas of my app where it would be nice to manually
control the ability to edit records if they are in use by another user.  Is
there a way to manually check and see if a particular record is in use or
manually lock a record so it cannot be edited by another user even when
utilizing Optimistic locking?

Thanks in advance.

Brian Kennedy

Brian

I don´t know if is a good design but I use a special field I fill *BEFORE*
edit and clear just after POST. If this field contain some information then
it is used by another user. It works ok but in situations like power down
you need to create a special function to unlock all records, IOW clear the
values of this field in ALL records.

Eduardo

Brian,

<< However, there are some areas of my app where it would be nice to
manually control the ability to edit records if they are in use by another
user.  Is there a way to manually check and see if a particular record is in
use or manually lock a record so it cannot be edited by another user even
when utilizing Optimistic locking? >>

Unfortunately, no.  You must switch to pessimistic locking in order to allow
an Edit to obtain a record lock.  However, don't switch the record lock
protocol while the application has edits in progress or you could run into
problems.

--
Tim Young
Elevate Software
www.elevatesoft.com

Presumably if the extra field was a "lock time field" then you could
simply automatically expire a lock if it had been locked for too long?

/Matthew Jones/

"Brian Kennedy" <briank@mtcpro.com> wrote in message
news:8B059145-12F0-4DAF-8F3D-C5E89D940B46@news.elevatesoft.com...
> Hi.  Using DBISAM Version 4.24 Build #1.  Due to the nature of my
> application and how some of the automation features operate, I need to use
> Optimistic record locking.
>
> However, there are some areas of my app where it would be nice to manually
> control the ability to edit records if they are in use by another user.

If the record id or some other unique numeric field (even if it is
calculated) on each record to be locked is less than 1000, you can use
semaphores. Place a semaphore when you start editing, and test the semaphore
before you edit.

In fact, you do not need to edit the record, since this will be all your
logic and not dependent on the DBISAM engine at all. I have a couple of apps
where my logic requires that if an operator is reviewing or updating a
certain customer, that customer (ALL its data) should be blocked from all
other operators. Since my customer numbers are all under 1000, semaphores
are an easy solution and they go away when the application ends.

Robert

Matthew

Yep. It would be a solution too.

Eduardo

Thanks for all of your input.  It is very helpful.  I think Jose's option
would work best for this scenario as the table contains well over 1,000
records.

Once more question for Tim before I proceed:

-User 1 opens a record for modification.
- While User 1 is editing the record, User 2 opens the SAME RECORD, makes a
change, and saves.
- User 1 clicks SAVE and a DBISAM exception occurs because the record has
been altered by User 2.

Question:  Is there a way to force a save on User #1's record anyway?

Thank you.

Brian

"Brian Kennedy" <briank@mtcpro.com> wrote in message
news:8B059145-12F0-4DAF-8F3D-C5E89D940B46@news.elevatesoft.com...
> Hi.  Using DBISAM Version 4.24 Build #1.  Due to the nature of my
> application and how some of the automation features operate, I need to use
> Optimistic record locking.
>
> However, there are some areas of my app where it would be nice to manually
> control the ability to edit records if they are in use by another user.
> Is there a way to manually check and see if a particular record is in use
> or manually lock a record so it cannot be edited by another user even when
> utilizing Optimistic locking?
>
> Thanks in advance.
>
> Brian Kennedy
>

Brian

> -User 1 opens a record for modification.
> - While User 1 is editing the record, User 2 opens the SAME RECORD, makes
> a change, and saves.
> - User 1 clicks SAVE and a DBISAM exception occurs because the record has
> been altered by User 2.
>
> Question:  Is there a way to force a save on User #1's record anyway?

The only way to do this is trapping the error, save the current record
values, apply a Refresh, update the fields with fields saved and post again.

Eduardo

Brian,

<< Question:  Is there a way to force a save on User #1's record anyway? >>

Eduardo is correct.  EDB allows this via the
TEDBSession.RecordChangeDetection property which controls whether row
changes raise an exception or not.

--
Tim Young
Elevate Software
www.elevatesoft.com