Multi-user concurrency

Does anyone have links to various strategies for handling multi-user concurrency issues when updating data in SQL Server (2000 or 2005), either in the database (stored procedures) or via code.

I've seen a couple such as:

Check individual user updated columns to see if the database columns have changed and if not apply the updated columns (either individual updates or constructing a dynamic SQL statement).

Check all the fields for any change and if no change, update all the fields.

Check a version field for change and if no change, update all the fields.

What I haven't seen is complete solutions such as for the first one, ensuring the record is locked and can't be changed while checking for concurrency and ultimately updating the data. For the second one, how to raise an error if there was a problem, or for the third one how to ensure the record is locked between the version check and the update.

Even pieces of solutions are welcome (locking records, testing for change, etc). Just want to compare and contrast various methods as I create an infrastructure for 2005.

Thanks,

LarryC

SQL Server itself can control such concurrency. If you just want to lock the data when updating, the default trancation isolation level 'READ COMMITTED' is enough, you can refer to:http://msdn.microsoft.com/library/default.asp?url=/library/en-us/tsqlref/ts_set-set_74bw.asp

Is this what you want?

|||

That might work in conjunction with some of the samples I've seen to ensure the record can't change between checks, thansk!. I was looking for end-to-end strategies that various people have used to implement multi-user concurrency in their apps/databases. I'm guessing this is a common problem with a number of solutions, some of which are likely to be better than others in various senarios.

Also in conjunction with the method for ensuring the database doesn't change between test and update, do you have any samples of how to handle the possible resulting errors or tips on how to reduce/elminate errors? Currently I'm planning on doing updats and deletes from the bottom up and for tables at the same general level applying updates/deletes alphabetically (hoping to eliminate blocking locks) but any insight into issues or examples of solutions would be greatly appreciated.

Multiple Transaction Logs

Hey Folks,
I was looking for some documents/articles/links to get a better
understanding of Multiple Transaction Logs for SQL Server 2000/7. For
example, if I create two transaction logs for a database, how are they used?
Round-Robin method until each one is full? Or use one at a time until the
second log file is needed?
I also wanted to learn about backing up and restore multiple transaction
logs. How to delete the second log file? Is one log active and the other
in-active, etc.
Hope to get some good reading material.
Thanks,
DeeJay
DeeJay,
Have you looked in Books Online? I think that there's a pretty good section about these things. Not
that complicated, though:

> For
> example, if I create two transaction logs for a database, how are they used?
> Round-Robin method until each one is full? Or use one at a time until the
> second log file is needed?
One at a time. Think about the log as a snake rattling though the file(s). Each time you backup log,
you cut the tail of the snake. If you have several files, and you are at then end of the current
file (and it is full), the head of the snake moves to the beginning of the next file.

> I also wanted to learn about backing up and restore multiple transaction
> logs.
You don't backup the log file. You perform a transaction log backup for the database. To SQL Server,
the transaction log is one logical construct (which happens to be spread out over several physical
files). At restore, though, you need to have as many files as when you performed the backup.

> How to delete the second log file?
DBCC SHRINKFILE with the EMPTYFILE option. Make sure it is empty. Then ALTER DATABASE to remove it.

> Is one log active and the other
> in-active, etc.
Not the files per se.
One thing you want to look into is the concept of VLF (Virtual Log Files). The log file is divided
up in a number of VLF, and a VLF can be active (log records on it) or inactive (empty, not used).
Use DBCC LOGINFO for this. I mention a little bit about this in
http://www.karaszi.com/SQLServer/info_dont_shrink.asp.
Tibor Karaszi, SQL Server MVP
http://www.karaszi.com/sqlserver/default.asp
http://www.solidqualitylearning.com/
http://www.sqlug.se/
"DeeJay Puar" <DeeJayPuar@.discussions.microsoft.com> wrote in message
news:8F52396F-1FBA-468C-B5C4-11BF4BDDB720@.microsoft.com...
> Hey Folks,
> I was looking for some documents/articles/links to get a better
> understanding of Multiple Transaction Logs for SQL Server 2000/7. For
> example, if I create two transaction logs for a database, how are they used?
> Round-Robin method until each one is full? Or use one at a time until the
> second log file is needed?
> I also wanted to learn about backing up and restore multiple transaction
> logs. How to delete the second log file? Is one log active and the other
> in-active, etc.
> Hope to get some good reading material.
> Thanks,
> DeeJay
|||Tibor,
Thanks for the reply.
I was already familiar with these concepts (the snake analogy is a good
one). I am also familiar with the VLFs.
I was not sure about deleting the EMPTY log files. Thanks for that.
Thanks for the undocumented DBCC LOGINFO command!
I am getting cross-trained in DB2 and DB2 has a slightly different way of
handling its transaction logs (hence the terminology active/inactive). The
DB2 DBA had asked about it and I wanted to make sure I was able to explain it
to him properly.
Thanks,
DeeJay
"Tibor Karaszi" wrote:

> DeeJay,
> Have you looked in Books Online? I think that there's a pretty good section about these things. Not
> that complicated, though:
>
> One at a time. Think about the log as a snake rattling though the file(s). Each time you backup log,
> you cut the tail of the snake. If you have several files, and you are at then end of the current
> file (and it is full), the head of the snake moves to the beginning of the next file.
>
> You don't backup the log file. You perform a transaction log backup for the database. To SQL Server,
> the transaction log is one logical construct (which happens to be spread out over several physical
> files). At restore, though, you need to have as many files as when you performed the backup.
>
> DBCC SHRINKFILE with the EMPTYFILE option. Make sure it is empty. Then ALTER DATABASE to remove it.
>
> Not the files per se.
> One thing you want to look into is the concept of VLF (Virtual Log Files). The log file is divided
> up in a number of VLF, and a VLF can be active (log records on it) or inactive (empty, not used).
> Use DBCC LOGINFO for this. I mention a little bit about this in
> http://www.karaszi.com/SQLServer/info_dont_shrink.asp.
> --
> Tibor Karaszi, SQL Server MVP
> http://www.karaszi.com/sqlserver/default.asp
> http://www.solidqualitylearning.com/
> http://www.sqlug.se/
>
> "DeeJay Puar" <DeeJayPuar@.discussions.microsoft.com> wrote in message
> news:8F52396F-1FBA-468C-B5C4-11BF4BDDB720@.microsoft.com...
>
>

Multiple Transaction Logs

Hey Folks,
I was looking for some documents/articles/links to get a better
understanding of Multiple Transaction Logs for SQL Server 2000/7. For
example, if I create two transaction logs for a database, how are they used?
Round-Robin method until each one is full? Or use one at a time until the
second log file is needed?
I also wanted to learn about backing up and restore multiple transaction
logs. How to delete the second log file? Is one log active and the other
in-active, etc.
Hope to get some good reading material.
Thanks,
DeeJayDeeJay,
Have you looked in Books Online? I think that there's a pretty good section
about these things. Not
that complicated, though:

> For
> example, if I create two transaction logs for a database, how are they use
d?
> Round-Robin method until each one is full? Or use one at a time until the
> second log file is needed?
One at a time. Think about the log as a snake rattling though the file(s). E
ach time you backup log,
you cut the tail of the snake. If you have several files, and you are at the
n end of the current
file (and it is full), the head of the snake moves to the beginning of the n
ext file.

> I also wanted to learn about backing up and restore multiple transaction
> logs.
You don't backup the log file. You perform a transaction log backup for the
database. To SQL Server,
the transaction log is one logical construct (which happens to be spread out
over several physical
files). At restore, though, you need to have as many files as when you perfo
rmed the backup.

> How to delete the second log file?
DBCC SHRINKFILE with the EMPTYFILE option. Make sure it is empty. Then ALTER
DATABASE to remove it.

> Is one log active and the other
> in-active, etc.
Not the files per se.
One thing you want to look into is the concept of VLF (Virtual Log Files). T
he log file is divided
up in a number of VLF, and a VLF can be active (log records on it) or inacti
ve (empty, not used).
Use DBCC LOGINFO for this. I mention a little bit about this in
http://www.karaszi.com/SQLServer/info_dont_shrink.asp.
--
Tibor Karaszi, SQL Server MVP
http://www.karaszi.com/sqlserver/default.asp
http://www.solidqualitylearning.com/
http://www.sqlug.se/
"DeeJay Puar" <DeeJayPuar@.discussions.microsoft.com> wrote in message
news:8F52396F-1FBA-468C-B5C4-11BF4BDDB720@.microsoft.com...
> Hey Folks,
> I was looking for some documents/articles/links to get a better
> understanding of Multiple Transaction Logs for SQL Server 2000/7. For
> example, if I create two transaction logs for a database, how are they use
d?
> Round-Robin method until each one is full? Or use one at a time until the
> second log file is needed?
> I also wanted to learn about backing up and restore multiple transaction
> logs. How to delete the second log file? Is one log active and the other
> in-active, etc.
> Hope to get some good reading material.
> Thanks,
> DeeJay|||Tibor,
Thanks for the reply.
I was already familiar with these concepts (the snake analogy is a good
one). I am also familiar with the VLFs.
I was not sure about deleting the EMPTY log files. Thanks for that.
Thanks for the undocumented DBCC LOGINFO command!
I am getting cross-trained in DB2 and DB2 has a slightly different way of
handling its transaction logs (hence the terminology active/inactive). The
DB2 DBA had asked about it and I wanted to make sure I was able to explain i
t
to him properly.
Thanks,
DeeJay
"Tibor Karaszi" wrote:

> DeeJay,
> Have you looked in Books Online? I think that there's a pretty good sectio
n about these things. Not
> that complicated, though:
>
> One at a time. Think about the log as a snake rattling though the file(s).
Each time you backup log,
> you cut the tail of the snake. If you have several files, and you are at t
hen end of the current
> file (and it is full), the head of the snake moves to the beginning of the
next file.
>
> You don't backup the log file. You perform a transaction log backup for th
e database. To SQL Server,
> the transaction log is one logical construct (which happens to be spread o
ut over several physical
> files). At restore, though, you need to have as many files as when you per
formed the backup.
>
> DBCC SHRINKFILE with the EMPTYFILE option. Make sure it is empty. Then ALT
ER DATABASE to remove it.
>
> Not the files per se.
> One thing you want to look into is the concept of VLF (Virtual Log Files).
The log file is divided
> up in a number of VLF, and a VLF can be active (log records on it) or inac
tive (empty, not used).
> Use DBCC LOGINFO for this. I mention a little bit about this in
> http://www.karaszi.com/SQLServer/info_dont_shrink.asp.
> --
> Tibor Karaszi, SQL Server MVP
> http://www.karaszi.com/sqlserver/default.asp
> http://www.solidqualitylearning.com/
> http://www.sqlug.se/
>
> "DeeJay Puar" <DeeJayPuar@.discussions.microsoft.com> wrote in message
> news:8F52396F-1FBA-468C-B5C4-11BF4BDDB720@.microsoft.com...
>
>

Multiple Transaction Logs

Hey Folks,
I was looking for some documents/articles/links to get a better
understanding of Multiple Transaction Logs for SQL Server 2000/7. For
example, if I create two transaction logs for a database, how are they used?
Round-Robin method until each one is full? Or use one at a time until the
second log file is needed?
I also wanted to learn about backing up and restore multiple transaction
logs. How to delete the second log file? Is one log active and the other
in-active, etc.
Hope to get some good reading material.
Thanks,
DeeJayDeeJay,
Have you looked in Books Online? I think that there's a pretty good section about these things. Not
that complicated, though:
> For
> example, if I create two transaction logs for a database, how are they used?
> Round-Robin method until each one is full? Or use one at a time until the
> second log file is needed?
One at a time. Think about the log as a snake rattling though the file(s). Each time you backup log,
you cut the tail of the snake. If you have several files, and you are at then end of the current
file (and it is full), the head of the snake moves to the beginning of the next file.
> I also wanted to learn about backing up and restore multiple transaction
> logs.
You don't backup the log file. You perform a transaction log backup for the database. To SQL Server,
the transaction log is one logical construct (which happens to be spread out over several physical
files). At restore, though, you need to have as many files as when you performed the backup.
> How to delete the second log file?
DBCC SHRINKFILE with the EMPTYFILE option. Make sure it is empty. Then ALTER DATABASE to remove it.
> Is one log active and the other
> in-active, etc.
Not the files per se.
One thing you want to look into is the concept of VLF (Virtual Log Files). The log file is divided
up in a number of VLF, and a VLF can be active (log records on it) or inactive (empty, not used).
Use DBCC LOGINFO for this. I mention a little bit about this in
http://www.karaszi.com/SQLServer/info_dont_shrink.asp.
--
Tibor Karaszi, SQL Server MVP
http://www.karaszi.com/sqlserver/default.asp
http://www.solidqualitylearning.com/
http://www.sqlug.se/
"DeeJay Puar" <DeeJayPuar@.discussions.microsoft.com> wrote in message
news:8F52396F-1FBA-468C-B5C4-11BF4BDDB720@.microsoft.com...
> Hey Folks,
> I was looking for some documents/articles/links to get a better
> understanding of Multiple Transaction Logs for SQL Server 2000/7. For
> example, if I create two transaction logs for a database, how are they used?
> Round-Robin method until each one is full? Or use one at a time until the
> second log file is needed?
> I also wanted to learn about backing up and restore multiple transaction
> logs. How to delete the second log file? Is one log active and the other
> in-active, etc.
> Hope to get some good reading material.
> Thanks,
> DeeJay|||Tibor,
Thanks for the reply.
I was already familiar with these concepts (the snake analogy is a good
one). I am also familiar with the VLFs.
I was not sure about deleting the EMPTY log files. Thanks for that.
Thanks for the undocumented DBCC LOGINFO command!
I am getting cross-trained in DB2 and DB2 has a slightly different way of
handling its transaction logs (hence the terminology active/inactive). The
DB2 DBA had asked about it and I wanted to make sure I was able to explain it
to him properly.
Thanks,
DeeJay
"Tibor Karaszi" wrote:
> DeeJay,
> Have you looked in Books Online? I think that there's a pretty good section about these things. Not
> that complicated, though:
> > For
> > example, if I create two transaction logs for a database, how are they used?
> > Round-Robin method until each one is full? Or use one at a time until the
> > second log file is needed?
> One at a time. Think about the log as a snake rattling though the file(s). Each time you backup log,
> you cut the tail of the snake. If you have several files, and you are at then end of the current
> file (and it is full), the head of the snake moves to the beginning of the next file.
>
> > I also wanted to learn about backing up and restore multiple transaction
> > logs.
> You don't backup the log file. You perform a transaction log backup for the database. To SQL Server,
> the transaction log is one logical construct (which happens to be spread out over several physical
> files). At restore, though, you need to have as many files as when you performed the backup.
>
> > How to delete the second log file?
> DBCC SHRINKFILE with the EMPTYFILE option. Make sure it is empty. Then ALTER DATABASE to remove it.
> > Is one log active and the other
> > in-active, etc.
> Not the files per se.
> One thing you want to look into is the concept of VLF (Virtual Log Files). The log file is divided
> up in a number of VLF, and a VLF can be active (log records on it) or inactive (empty, not used).
> Use DBCC LOGINFO for this. I mention a little bit about this in
> http://www.karaszi.com/SQLServer/info_dont_shrink.asp.
> --
> Tibor Karaszi, SQL Server MVP
> http://www.karaszi.com/sqlserver/default.asp
> http://www.solidqualitylearning.com/
> http://www.sqlug.se/
>
> "DeeJay Puar" <DeeJayPuar@.discussions.microsoft.com> wrote in message
> news:8F52396F-1FBA-468C-B5C4-11BF4BDDB720@.microsoft.com...
> > Hey Folks,
> >
> > I was looking for some documents/articles/links to get a better
> > understanding of Multiple Transaction Logs for SQL Server 2000/7. For
> > example, if I create two transaction logs for a database, how are they used?
> > Round-Robin method until each one is full? Or use one at a time until the
> > second log file is needed?
> >
> > I also wanted to learn about backing up and restore multiple transaction
> > logs. How to delete the second log file? Is one log active and the other
> > in-active, etc.
> >
> > Hope to get some good reading material.
> >
> > Thanks,
> >
> > DeeJay
>
>