Log shipping breaks what to do now :
----------------------------------------------------------
1.
Either
we can reconfigure log shipping using full and log backup.
2.
Or
if lucky we can take one differential backup and keep log shipping active but
there is a catch:
We must make sure there is no full backup
performed on primary database after log shipping breaks and before taking
differential backup.Reason :
A differential backup can be restored on database
a. After last full back up has been restored on secondary server with norecovery or
b. Any previous(old) full backup together with all subsequent log backup and atleast one log backup after last full backup and before final diff backup taken has been restored before another full backup
Consider
the following scenario for restoring differential backup (DF3) take at today (T) at 7 PM
DB1 DB2|
Backup type (Base
LSN)
|
Time
|
Restored database
(Base LSN)
|
|
Full backup (..031) FB1
|
T-10
|
(..031)
|
|
Log backup (..031)
LB1
|
T-9
|
(..031)
|
|
Log backup (..031)
LB2
|
T-8
|
(..031)
|
|
Diff backup (..031) DB1
|
T-7
|
(..031)
|
|
Full backup (..045) FB2
|
T-6
|
Not restored (..031)
|
|
Log backup (..045) LB3
|
T-5
|
(..045)
|
|
Log backup (..045) LB4
|
T-4
|
(..045)
|
|
Full
backup (..056) FB3
|
T-1
|
Not
restored (..45)
|
Assume no
other backup taken apart from above backup and diff backup taken today.
We can
restore diff backup (DF3) if
1.
FB3
backup not taken (FB1 + LB1+LB2+LB3+LB4) + DF3
2.
FB3
backup not taken (FB1 + LB1+LB2+LB3) + DF3
3.
FB3
backup not taken (FB2+ LB3+LB4) + DF3
4.
FB3
backup not taken (FB2+ LB3) + DF3
5.
FB3
backup not taken (FB2) + DF3
6.
FB3
backup taken but not restored DF3 won’t work with any combination and will be
invalid until we restore the FB3.
what this
means is that, as long as log backups are restored to the secondary, the
Differential base LSN remains in step allowing you to bridge LSN gaps between
the primary and the secondary databases using a differential backup.
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