BACKUP CURRENT CONTROLFILE creates a Snapshot Controlfile

Recently, there was a discussion on forums about when a Snapshot controlfile is created.  It is known that the snapshot controlfile is created to re-synchronise with the Catalog.

But in my test database environment, I don't use a Catalog.  I only use the controlfile (and backups of it).

One poser said that he ran BACKUP DATABASE followed by BACKUP CURRENT CONTROLFILE. He asked if the same snapshot controlfile was used [through the two commands].  I pointed out that since they were two *separate* BACKUP calls, Oracle would create a separate Snapshot Controlfile for the second BACKUP command.

Here is a simple demo (note : I don't use a Catalog)

First the current state of the directory ($ORACLE_HOME/dbs in my case) where the Snapshot Controlfile would be created :

[oracle@localhost dbs]$ pwd

/home/oracle/app/oracle/product/11.2.0/dbhome_2/dbs

[oracle@localhost dbs]$ date

Thu Mar 20 08:17:46 PDT 2014

[oracle@localhost dbs]$ ls -ltr|tail -3

-rw-r----- 1 oracle oracle 1536 Oct  2  2010 orapworcl

-rw-rw---- 1 oracle oracle 1544 Mar 20 08:16 hc_orcl.dat

-rw-r----- 1 oracle oracle 3584 Mar 20 08:16 spfileorcl.ora

There is no snapshot currently present. 

Next, I run a BACKUP CURRENT CONTROLFILE :

[oracle@localhost dbs]$ rman target /

Recovery Manager: Release 11.2.0.2.0 - Production on Thu Mar 20 08:17:53 2014

Copyright (c) 1982, 2009, Oracle and/or its affiliates.  All rights reserved.

connected to target database: ORCL (DBID=1229390655)

RMAN> backup current controlfile;

Starting backup at 20-MAR-14

using target database control file instead of recovery catalog

allocated channel: ORA_DISK_1

channel ORA_DISK_1: SID=69 device type=DISK

channel ORA_DISK_1: starting full datafile backup set

channel ORA_DISK_1: specifying datafile(s) in backup set

including current control file in backup set

channel ORA_DISK_1: starting piece 1 at 20-MAR-14

channel ORA_DISK_1: finished piece 1 at 20-MAR-14

piece handle=/home/oracle/app/oracle/flash_recovery_area/ORCL/backupset/2014_03_20/o1_mf_ncnnf_TAG20140520T081800_8snhob80_.bkp tag=TAG20140320T081800 comment=NONE

channel ORA_DISK_1: backup set complete, elapsed time: 00:00:01

Finished backup at 20-MAR-14

RMAN> quit

Recovery Manager complete.

The controlfile backup got written to the FRA.

 Is there a snapshot controlfile ?

[oracle@localhost dbs]$ ls -ltr|tail -3

-rw-rw---- 1 oracle oracle    1544 Mar 20 08:16 hc_orcl.dat

-rw-r----- 1 oracle oracle    3584 Mar 20 08:16 spfileorcl.ora

-rw-rw---- 1 oracle oracle 9748480 Mar 20 08:18 snapcf_orcl.f

[oracle@localhost dbs]$

Yes, a snapshot controlfile did get created !