The reason you need a new, clean backup is that you must have all of the
committed transactions as part of the backup, including the database and the active
transaction log. If a log backup occurs before you back up the database, you??™ll receive
an error later when you try to enable mirroring.
CHAPTER 8 n DATABASE MIRRORING 211
nTip Creating a full backup resets your LSN chain as it relates to differential backups, but there??™s a way
around that. Do you remember the WITH COPY_ONLY clause back in Chapter 2? Now is the perfect example
of when you should use it.
Next, copy the backup to the instance you want to use for the mirror database (in
this case, it??™s on the same PC) and restore it. Read that last sentence carefully, because
it??™s important. You??™re restoring the database, but you??™re not recovering the database. You
need to leave the mirror database in a state where it can continue to receive new
records, as shown in Figure 8-11.
Figure 8-11. Before configuring any level of database mirroring, you must prepare a suitable
mirror database and leave it in a state ready for additional transaction logs.
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