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sql server programming : Locking question
[quoted text, click to view] <ca6lma@Hotmail.com> wrote: >from vb6 using unbound forms i call a stored procedures which include just a >select statement like > >select * from users where userId = @userId > >Always return one row. > >My question is how i can determine if this record is locked regardsless of >whether it will be changed or not; just to avoid complications > >I want to use this in the case another user want to edit the same record and >hence running the same procedure. Oh, what you asked! The recommended approach to most modern database usage is "optimistic" locking, in which you do something like taking the timestamp from the record you read and use it if and when you decide to do an update. The server can then reject your update, saying "someone beat you to it." This is acceptable if it happens rarely enough, and in many cases, that is the statistical situation. So, generally, records are not detectably locked at all! Now, if you're an old fart like myself and still prefer to do what they call "pessimistic" locking now and again, SQLServer does support this, but the only way I know of detecting it, is to attempt to lock it yourself. If your lock is issued, you got it, and if it is rejected, someone else does. There are good and bad ways to go about this all, of course. You could attempt the lock and release it if you get it, but ... well, you see the tangles that result. To attempt such a lock, do a begin trans, then do a select "with (updlock)". Since even SQLServer actually does lock records at some point, especially in big, fat transactions, your update detection may indeed detect some locked records, even if they are only implicitly locked for very short periods in most cases. Though, in general, you seldom need to or want to know about such things. See BOL for more details on stuff like updlock. Best of luck, J.
from vb6 using unbound forms i call a stored procedures which include just a
select statement like select * from users where userId = @userId Always return one row. My question is how i can determine if this record is locked regardsless of whether it will be changed or not; just to avoid complications I want to use this in the case another user want to edit the same record and hence running the same procedure.
Additionally, if you want to be able to just read the row, and are not
concerned about that data being updated by another user who currently has the same row "locked" you can use select * from tablename (nolock) hint. Stu [quoted text, click to view] "JXStern" <JXSternChangeX2R@gte.net> wrote in message news:2s37lvkfbkkplo4u5fn80hgon8ffkvq4nn@4ax.com... > On Mon, 1 Sep 2003 20:52:21 +0300, "Loukas Marinis" > <ca6lma@Hotmail.com> wrote: > >from vb6 using unbound forms i call a stored procedures which include just a > >select statement like > > > >select * from users where userId = @userId > > > >Always return one row. > > > >My question is how i can determine if this record is locked regardsless of > >whether it will be changed or not; just to avoid complications > > > >I want to use this in the case another user want to edit the same record and > >hence running the same procedure. > > Oh, what you asked! > > The recommended approach to most modern database usage is "optimistic" > locking, in which you do something like taking the timestamp from the > record you read and use it if and when you decide to do an update. > The server can then reject your update, saying "someone beat you to > it." This is acceptable if it happens rarely enough, and in many > cases, that is the statistical situation. > > So, generally, records are not detectably locked at all! > > Now, if you're an old fart like myself and still prefer to do what > they call "pessimistic" locking now and again, SQLServer does support > this, but the only way I know of detecting it, is to attempt to lock > it yourself. If your lock is issued, you got it, and if it is > rejected, someone else does. There are good and bad ways to go about > this all, of course. You could attempt the lock and release it if you > get it, but ... well, you see the tangles that result. To attempt > such a lock, do a begin trans, then do a select "with (updlock)". > > Since even SQLServer actually does lock records at some point, > especially in big, fat transactions, your update detection may indeed > detect some locked records, even if they are only implicitly locked > for very short periods in most cases. Though, in general, you seldom > need to or want to know about such things. > > See BOL for more details on stuff like updlock. > > Best of luck, > J. >
Thanx for your help. I was a bit aware of what you mention and eventually
seems that timestamp is a good solution. However i was looking for a pessimistic solution. A bit of background Let's suppose there is a listview with all the users. when i click one user, a new form is opening, the required stored procedure is running(as we said before) and the corresponding fields are filled. My question is: The Lock is released as soon as the stored procedure is completed? Can i somehow define when to release the lock(in my case when i close the form) or by other means? [quoted text, click to view] "JXStern" <JXSternChangeX2R@gte.net> wrote in message news:2s37lvkfbkkplo4u5fn80hgon8ffkvq4nn@4ax.com... > On Mon, 1 Sep 2003 20:52:21 +0300, "Loukas Marinis" > <ca6lma@Hotmail.com> wrote: > >from vb6 using unbound forms i call a stored procedures which include just a > >select statement like > > > >select * from users where userId = @userId > > > >Always return one row. > > > >My question is how i can determine if this record is locked regardsless of > >whether it will be changed or not; just to avoid complications > > > >I want to use this in the case another user want to edit the same record and > >hence running the same procedure. > > Oh, what you asked! > > The recommended approach to most modern database usage is "optimistic" > locking, in which you do something like taking the timestamp from the > record you read and use it if and when you decide to do an update. > The server can then reject your update, saying "someone beat you to > it." This is acceptable if it happens rarely enough, and in many > cases, that is the statistical situation. > > So, generally, records are not detectably locked at all! > > Now, if you're an old fart like myself and still prefer to do what > they call "pessimistic" locking now and again, SQLServer does support > this, but the only way I know of detecting it, is to attempt to lock > it yourself. If your lock is issued, you got it, and if it is > rejected, someone else does. There are good and bad ways to go about > this all, of course. You could attempt the lock and release it if you > get it, but ... well, you see the tangles that result. To attempt > such a lock, do a begin trans, then do a select "with (updlock)". > > Since even SQLServer actually does lock records at some point, > especially in big, fat transactions, your update detection may indeed > detect some locked records, even if they are only implicitly locked > for very short periods in most cases. Though, in general, you seldom > need to or want to know about such things. > > See BOL for more details on stuff like updlock. > > Best of luck, > J. >
How to find out if a table is locked:
[quoted text, click to view] "Loukas Marinis" <ca6lma@Hotmail.com> wrote in message news:eEju5HLcDHA.4020@tk2msftngp13.phx.gbl... > from vb6 using unbound forms i call a stored procedures which include just a > select statement like > > select * from users where userId = @userId > > Always return one row. > > My question is how i can determine if this record is locked regardsless of > whether it will be changed or not; just to avoid complications > > I want to use this in the case another user want to edit the same record and > hence running the same procedure. > > > >
Here's how to list all the locks on a table:
select distinct page, type, spid from master.dbo.syslocks where dbid = db_id() and id = object_id('dbo.Table1') [quoted text, click to view] "Loukas Marinis" <ca6lma@Hotmail.com> wrote in message news:eEju5HLcDHA.4020@tk2msftngp13.phx.gbl... > from vb6 using unbound forms i call a stored procedures which include just a > select statement like > > select * from users where userId = @userId > > Always return one row. > > My question is how i can determine if this record is locked regardsless of > whether it will be changed or not; just to avoid complications > > I want to use this in the case another user want to edit the same record and > hence running the same procedure. > > > >
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