On 22/04/2015 4:38 PM, Mladen Gogala (Redacted sender mgogala@xxxxxxxxx
for DMARC) wrote:
On 04/22/2015 11:06 AM, Hans Forbrich wrote:Glad we agree.
Hans, how does rman work? What happens when you do "allocate channel c0 device type SBT"? Several things happen:
Issue here is the definition of BackUp. Unfortunately, I have run across too many people who believe the RMAN executable actually does the work of backing up the database. My post was to allow access official references on the process.
As for central 'back up', the referenced doc mentions Oracle Secure Backup, which is also a centralized mechanism similar in nature to other commercial products. From that perspective, it is useful to look at Oracle's implementation of what you describe, and that is available at http://docs.oracle.com/cd/E16926_01/doc.121/e16564/osb_rman_backup.htm#OBADM187
* oracle process is allocated.
* MML library is mapped into the rman address space
* sbtinit routine is executed to initialize the MML side of the channel.
After that, when a "backup" command is issued, Oracle process reads the database and delivers the data to the channel, possibly using Oracle*Net. The channel then pumps the data toward the backup software. That's the nature of the beast. The "rman" executable is a client, similar to sqlplus, which executes the internal functions, built into the Oracle executable itself and delivers the data to the destination using the channels. If the channels are defined using MML library ("device type SBT"), then the sbtwrite and sbtwrite2 routines are used to send the data to the backup software, be it NB, Avamar, Simpana or something else.
In other words, if there is a centralized node used to backup all the database by establishing remote connection to the database and opening channel toward backup software, that node is a critical point of failure.
