create procedure sys.sp_can_tlog_be_applied
(
@backup_file_name nvarchar(500)
,@database_name sysname
,@result bit = 0 output
,@verbose bit = 0
)
as
begin
set nocount on
declare @retcode int
,@command nvarchar(1000)
,@backup_type int
,@backupdbname sysname
,@backup_first_lsn numeric(25,0)
,@backup_last_lsn numeric(25,0)
,@db_redo_start_lsn numeric(25,0)
declare @backup_header table (
BackupName nvarchar(128) NULL,
BackupDescription nvarchar(256) NULL,
BackupType int,
ExpirationDate datetime NULL,
Compressed int,
Position int,
DeviceType int,
UserName nvarchar(128) NULL,
ServerName nvarchar(128),
DatabaseName nvarchar(128),
DatabaseVersion int,
DatabaseCreationDate datetime,
BackupSize numeric(20,0) NULL,
FirstLsn numeric(25,0) NULL,
LastLsn numeric(25,0) NULL,
CheckpointLsn numeric(25,0) NULL,
DatabaseBackupLsn numeric(25,0) NULL,
BackupStartDate datetime,
BackupFinishDate datetime,
SortOrder int,
CodePage int,
UnicodeLocaleId int,
UnicodeComparisonStyle int,
CompatibilityLevel int,
SoftwareVendorId int,
SoftwareVersionMajor int,
SoftwareVersionMinor int,
SoftwareVersionBuild int,
MachineName nvarchar(128),
Flags int NULL,
BindingId uniqueidentifier NULL,
RecoveryForkId uniqueidentifier NULL,
Collation nvarchar(128) null,
FamilyGUID uniqueidentifier null,
HasBulkLoggedData bit null,
IsSnapshot bit null,
IsReadOnly bit null,
IsSingleUser bit null,
HasBackupChecksums bit null,
IsDamaged bit null,
BeginsLogChain bit null,
HasIncompleteMetadata bit null,
IsForceOffline bit null,
IsCopyOnly bit null,
FirstRecoveryForkID uniqueidentifier null,
ForkPointLSN numeric(25,0) null,
RecoveryModel nvarchar(60) null,
DifferentialBaseLSN numeric(25,0) null,
DifferentialBaseGUID uniqueidentifier null,
BackupTypeDescription nvarchar(60) null,
BackupSetGUID uniqueidentifier null,
CompressedBackupSize numeric(20,0) null)
--
-- security check
--
exec @retcode = sys.sp_MSlogshippingsysadmincheck
if (@retcode != 0 or @@error != 0)
return 1
--
-- initialize
--
select @result = 0
--
-- get the backup information
--
select @command = N'restore headeronly from disk = N''' + replace(@backup_file_name, N'''',N'''''') + N''''
insert into @backup_header
execute(@command)
if (@@error != 0)
return 1
--
-- get the redo start lsn for the database
-- choose the smallest value from all of the files of the database being restored
-- State 0 is "online", so this handles page restore, or cases where the "restoring" state isn't marked properly.
-- State 1 is "restoring", which is the expected state.
-- redo_start_lsn is null for files which are not subject to restore.
--
select @db_redo_start_lsn = min(redo_start_lsn)
from master.sys.master_files
where database_id = db_id (@database_name)
and type = 0
and state in (0,1)
and redo_start_lsn is not null
if (@db_redo_start_lsn is null)
begin
--
-- the log can not be restored
--
return 0
end -- if (@db_redo_start_lsn is null)
if (@verbose = 1)
begin
raiserror('The redo start LSN for the database is:', 10, 1)
select @db_redo_start_lsn
end
--
-- Get the first LSN from backup header
-- Will need the other info for old method
--
select top 1 @backupdbname = DatabaseName
,@backup_first_lsn = ISNULL(FirstLsn, 0)
,@backup_last_lsn = ISNULL(LastLsn, 0)
,@backup_type = BackupType
from @backup_header
if (@verbose = 1)
begin
raiserror(N'The backup details (FirstLSN, LastLSN, BackupType, DatabaseName) :', 10, 1)
select @backup_first_lsn, @backup_last_lsn, @backup_type, @backupdbname
end
--
-- Basic sanity checks
--
if (@backupdbname != @database_name)
begin
raiserror(14418,10,1, @database_name)
end
if (@backup_type not in (1,2))
begin
raiserror(14419,-1,-1)
return (1) -- Failure
end
--
-- We can apply the backup if the
-- backup_first_lsn <= db_redo_start_lsn < backup_last_lsn
-- In strict sense - we can apply the backup if db_redo_start_lsn
-- is equal to backup_last_lsn, however no pages will be restored
-- The aim is to pick one log file that will satisfy the criterion for
-- applying restore
--
if (@db_redo_start_lsn >= @backup_first_lsn and @db_redo_start_lsn < @backup_last_lsn)
select @result = 1
--
-- all done
--
return 0
end
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