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Truncating Transaction Logs Expand / Collapse
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Posted Monday, March 7, 2005 2:26 PM


Old Hand

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Last Login: Friday, November 8, 2013 3:39 PM
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We are writing queries to determine if a transaction log was truncated since the last backup.  We have found a way to do this with the first and last lsn's.

 

BUT!!  Does anyone know if an entry is created in any database acknowledging that the transaction log was backed up with a TRUNCATE_ONLY command?

 

Thanks Everyone!!




"Keep Your Stick On the Ice" ..Red Green
Post #166113
Posted Tuesday, March 8, 2005 1:11 AM


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I guess not. Maybe it only comes available if the log is rolledover

I've tested this small sample, and the restore to the new db workd without a warning
So If there were any registration, the last log-restore should fail !

--
create database DTEST
go


BACKUP DATABASE DTEST
TO disk='c:\dtestfull.bak'
 WITH  INIT
go

use dtest
go

create table dbo.tttt(col1 int not null)
go

insert into dbo.tttt values(1)
go

backup log DTEST
TO disk='c:\dtestLog.bak'
 WITH  INIT

insert into dbo.tttt
select max(col1) + 1 from dbo.tttt
go
insert into dbo.tttt
select max(col1) + 1 from dbo.tttt
go
insert into dbo.tttt
select max(col1) + 1 from dbo.tttt
go

backup log DTEST
TO disk='c:\dtestLog.bak'
 WITH  NOINIT

-- --
-- -- The CREATE DATABASE process is allocating 0.63 MB on disk 'DTEST'.
-- -- The CREATE DATABASE process is allocating 0.49 MB on disk 'DTEST_log'.
-- -- Processed 80 pages for database 'DTEST', file 'DTEST' on file 1.
-- -- Processed 1 pages for database 'DTEST', file 'DTEST_log' on file 1.
-- -- BACKUP DATABASE successfully processed 81 pages in 0.057 seconds (11.515 MB/sec).
-- --
-- -- (1 row(s) affected)
-- --
-- -- Processed 1 pages for database 'DTEST', file 'DTEST_log' on file 1.
-- -- BACKUP LOG successfully processed 1 pages in 0.030 seconds (0.221 MB/sec).
-- --
-- -- (1 row(s) affected)
-- --
-- --
-- -- (1 row(s) affected)
-- --
-- --
-- -- (1 row(s) affected)
-- --
-- -- Processed 1 pages for database 'DTEST', file 'DTEST_log' on file 2.
-- -- BACKUP LOG successfully processed 1 pages in 0.030 seconds (0.051 MB/sec).


insert into dbo.tttt
select max(col1) + 1 from dbo.tttt
go

insert into dbo.tttt
select max(col1) + 1 from dbo.tttt
go
insert into dbo.tttt
select max(col1) + 1 from dbo.tttt
go

BACKUP LOG ddbastatistics WITH  truncate_only
go

insert into dbo.tttt
select max(col1) + 1 from dbo.tttt
go
insert into dbo.tttt
select max(col1) + 1 from dbo.tttt
go
insert into dbo.tttt
select max(col1) + 1 from dbo.tttt
go

backup log DTEST
TO disk='c:\dtestLog.bak'
 WITH  NOINIT
go
select max(col1) as max_col1, count(*) as No_Rows  from dbo.tttt

use master
go

declare @Logbackup_Filename varchar(500)
declare @Restore_New_DBname varchar(128)

select @Logbackup_Filename = 'c:\dtestLog.bak'
 , @Restore_New_DBname = 'DTEST1'

declare @RestoreDb_stmt varchar(5000)

select @RestoreDb_stmt = 'restore database ' + @Restore_New_DBname + '
FROM DISK = ''c:\dtestfull.bak''
 WITH MOVE N''DTEST'' TO N''U:\yourpath\Data\' + @Restore_New_DBname + '.mdf''
, MOVE N''DTEST_log'' TO N''S:\yourpath\Log\' + @Restore_New_DBname + '_log.LDF''
    , replace
    , NoRecovery '

exec (@RestoreDb_stmt)

if (select isnull( object_id(N'tempdb.[dbo].[#Tmp_BackupHeaders]'), 0)) <> 0
begin
 DROP table #Tmp_BackupHeaders
end

-- versie SQL2K sp3a
create table #Tmp_BackupHeaders (
BackupName nvarchar(128)
,BackupDescription  nvarchar(255)
,BackupType smallint
,ExpirationDate datetime
,Compressed tinyint
,Position smallint
,DeviceType tinyint
,UserName nvarchar(128)
,ServerName nvarchar(128)
,DatabaseName nvarchar(128)
,DatabaseVersion  int
,DatabaseCreationDate  datetime
,BackupSize numeric(20,0)
,FirstLSN numeric(25,0)
,LastLSN numeric(25,0)
,CheckpointLSN  numeric(25,0)
,DatabaseBackupLSN  numeric(25,0)
,BackupStartDate  datetime
,BackupFinishDate  datetime
,SortOrder smallint
,CodePage smallint
,UnicodeLocaleId int
, UnicodeComparisonStyle int
, CompatibilityLevel  tinyint
, SoftwareVendorId  int
,SoftwareVersionMajor  int
,SoftwareVersionMinor  int
,SoftwareVersionBuild  int
,MachineName nvarchar(128)
,Flags int
,BindingID uniqueidentifier
,RecoveryForkID uniqueidentifier
,Collation nvarchar(128)
)

declare @SQL varchar(5000)
set @SQL = 'RESTORE HEADERONLY FROM DISK = ''' + @Logbackup_Filename + ''' '

insert into #Tmp_BackupHeaders
exec (@SQL)

declare csrRestoreLog cursor  for
select 'print ''-- db [' + convert(varchar(128),DatabaseName) + '] -- ' + convert(varchar(15), Position)
+ ' -- LSN ' + convert(varchar(128), FirstLSN ) + ' <-> ' +  convert(varchar(128), LastLSN )
+ ' -- BackupDate ' + convert(varchar(25), BackupStartDate, 121) + ' <--> ' + convert(varchar(25), BackupFinishDate, 121)
+ ' ''' + char(13)
+ 'Restore Log ' + @Restore_New_DBname + '
FROM DISK = ''' + @Logbackup_Filename + '''
 WITH FILE = ' + convert(varchar(15),Position) + char(13)
+ case Position when M.MAX_Position then ' , Recovery '
  else ' , NoRecovery '
 end
-- + char(13) + 'GO'
from #Tmp_BackupHeaders
, (select max(Position) as MAX_Position from #Tmp_BackupHeaders ) M
order by Position

declare @RestoreLog_stmt varchar(5000)

open csrRestoreLog
FETCH NEXT FROM csrRestoreLog
 INTO @RestoreLog_stmt

WHILE @@FETCH_STATUS = 0
BEGIN

 exec (@RestoreLog_stmt)
 -- Volgende rij inlezen
 FETCH NEXT FROM csrRestoreLog
  INTO @RestoreLog_stmt

END


-- Cursor afsluiten
CLOSE csrRestoreLog
DEALLOCATE csrRestoreLog


go

select max(col1) as max_col1, count(*) as No_Rows  from DTEST1.dbo.tttt
go

 



Johan


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Post #166165
Posted Tuesday, March 8, 2005 7:58 AM


Old Hand

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Not what I expected.  Very interesting to say the least.   I wonder if throwing a CHECKPOINT at the database before the truncate would have effected the restore..Something doesn't seem right

 

Looks like I am going to play (test) today too.  Now my curiousity is going!!




"Keep Your Stick On the Ice" ..Red Green
Post #166234
Posted Tuesday, March 8, 2005 11:06 AM
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Alert 18278 fires when log gets truncated. You can configure this.




Post #166321
Posted Monday, May 16, 2005 11:17 AM
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Hi everybody,

I found this thread kind of late, but is only now that I've got the problem! I configured an alert on 18278 to net send a message when the transaction log is truncated for <mydb>. The alerts is  active, the operator to be notified is OK (receives notifications from other alerts and the test is sending the message).

Then I issued:

backup log mydb with truncate_only

I was expecting to see the pop-up window sent when the alert was fired, but nothing happened. I can see in SS2K error log that the log for that database was truncated but the alert didn't fire (Count shows 0 in the EM).

Can anybody help with an explanation?

Thanks,

Gabriela

Post #182713
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