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
>
>