Oracle/VMS Backup

I am trying to design a backup strategy for an Oracle7 database running on VAX/OpenVMS. I am experienced with VMS but new to Oracle 7. I hope someone out there can help me. I have read the very useful Oracle Backup FAQ. As far as possible, the system is required to provide as close to 24 hour 7 day availability and to provide recovery up to the last committed transaction in the event of media or software failure. It is accepted that it should be shut down at the weekend to allow a normal VMS image backups.

The database will be in ARCHIVELOG mode.

I am considering using the Oracle BEGIN BACKUP and END BACKUP commands to allow VMS BACKUP to copy the open database.

These are my concerns:

1. If I preserve the archived redo logs, do I need to worry about taking more frequent backups of the database?
2. Using BEGIN & END BACKUP:
3. what does Oracle do in this mode?
4. surely the backups will not be consistent if I backup tablespaces individually as recommended by the Backup FAQ?
5. are there any restrictions on user operations while in this mode?
6. The FAQ warns against putting all tablespaces into BEGIN BACKUP at the same time due to problems restoring if the system crashes. What are these problems?

Thanks for your time and help.  

  Ian G. Parker                Compuserve: [74170,1322]
  Hiredata Limited, London     Internet:   parker_at_hiredata.demon.co.uk