It's happening because of this statement:
backup log testdb1 to disk =N'C:\test\testdb1_log.bak' with norecovery
and here is the explanation from BOL:
NORECOVERY | STANDBY = undo_file_name }
NORECOVERY
Backs up the tail of the log and leaves the database in the RESTORING state. NORECOVERY is useful when failing over to a secondary database or when saving the tail of the log before a RESTORE operation.
To perform a best-effort log backup that skips log truncation and then take the database into the RESTORING state atomically, use the NO_TRUNCATE and NORECOVERY options together.
STANDBY = standby_file_name
Backs up the tail of the log and leaves the database in a read-only and STANDBY state. The STANDBY clause writes standby data (performing rollback, but with the option of further restores). Using the STANDBY option is equivalent to BACKUP LOG WITH NORECOVERY
followed by a RESTORE WITH STANDBY.
Using standby mode requires a standby file, specified by standby_file_name, whose location is stored in the log of the database. If the specified file already exists, the Database Engine overwrites it; if the file does not exist, the Database Engine creates
it. The standby file becomes part of the database.
This file holds the rolled back changes, which must be reversed if RESTORE LOG operations are to be subsequently applied. There must be enough disk space for the standby file to grow so that it can contain all the distinct pages from the database that were
modified by rolling back uncommitted transactions.
Harsh Chawla(MSFT) Personal Blog:-http://blogs.msdn.com/batala Team Blog:- http://blogs.msdn.com/b/sqlserverfaq/
