Locked row without error: A bug or a feature?

Forum|Forum|6 years ago
September 10, 2019
26 replies
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+3

Ingo Stiller
Participating Frequently

Hi freaks

Just found an awful bug or a great feature, I don't know ...
Say, there are 500 rows in database under a given profile
Row 200 may be locked by an update on database

Now retrieve all rows in UnifAce with the profile.
UnifAce will read up to 199 rows and then return.
$status is positiv 199 and not -11 for a locked row.

Okay, if the hitlist is shown to a customer, the is maybe a nice thing.
But under the hood as a service programm is very dangerous to go on without notification.

Is this a bug or a feature?
How to check, if there are more rows to come?

And no, I don't want to lock all rows that I read just to check if the hitlist is completed or not

Ingo

PS: UnifAce 9.704 on MS SQL

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+3

Ingo Stiller
Author
Participating Frequently
Forum|Forum|6 years ago
September 30, 2019

Hi Gianni

Ever do account software? 🙂
Lets have the following szenario:

One desk offizier starts a transaction about acount side transfer of money.
But he did not commit
Now he starts a second session and start the credit transfer to his bank account
The proper account record is aval (locked but avail)
After the transfer to the bank is done, he rollback the first session.

Nobody see the account record wich lead to the credit transfer

Another szenario
One clerk creates mass of account records by a weekly run. This run is still ongoing without a commit.
Another clerk runs a report against the database.
Wow we got thousend of euros at the end of the week, I have to report my boss.
But then there went something wrong at the first session and the bookings will be rolled back.

How's to blame ... 🙂

Ingo

Hi Gianni

Yes, I already got an email about this entry.
The workarounds are "nice"

a) Set the database to "snapshot isolation": Much to heavy for simple reads

b) Set MLW greater then "locktime":
A real lock should only last for a second, a long runnig script could take a "few" seconds.
So it's not a good idea to set MLW to more then 2 seconds

Ingo