John Mitchell-245523 (1/8/2013)
Do you happen to know whether it also applies if, for example, the LDF and MDF were backed up using open file agents?
Yes I do, and no it doesn't.
Unless the file backup tool either quiesced the IOs prior to the backup or somehow managed to copy the files at exactly the same nanosecond, there's a chance that the files are as of different points in time (small difference, but that's all it takes), and will fail to attach. If the log file was copied a smidgen later than the data file, the resultant files will probably attach. If the data file was copied a smidgen later than the log file, the resultant files probably won't attach.
Files that are copied when SQL is stopped or when the DB is offline or detached are static. Files that are copied while the database is active are not, and that's what may well make them not attach.
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