Cold backup downtime using RMAN

Question

Over the weekend I performed a cold RMAN backup on a 3.6 TB
database. Because a lot of the database was backed up with
transportable tablespaces, the net amount being backed up was
approximately 365 Gb. I took down the database at 11:00 and the
script finished at 4am, but in reviewing the logs, the database
actually appears to have been opened at 2am.
I assumed that the database would be down the entirety of the
backup. Can anyone help me understand why the database was
opened so long before the RMAN command completed? Was the
backup adversely affected in any way by a user obtaining access
prior to the RMAN process completing.
Any information greatly appreciated.

Answer 1

unfortunately i think you misunderstood the original question. i took the database down to do the cold backup. in order to use rman, you have to startup nomount the instance.
the script run was:
#!/usr/bin/ksh
rman msglog '/data2/oracle2/local/log/rman_lvl0.log' <<EOF
@connect.rman
run {
backup incremental level 0 tag full_bkup0 database diskratio=0;
alter database open;
exit;
EOF
exit
the "alter database open" tells RMAN to open the database once the backup is completed. i had a process running that checked each 10 seconds to see if the PID for the RMAN process was still running. The process itself appears to have run for an additional 2 hours after the database was opened.
there is nothing on the system to suggest that the database was opened by anything other than RMAN. was the database opened prematurely? was the additional time spent in the RMAN script doing the sync in the database? did the usage by the user prior to RMAN completing invalidate the backup? (so far the cloning is still running without error).