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 Mon May 20 08:17:46 PDT 2013 [oracle@localhost dbs]$ ls -ltr|tail -3 -rw-r----- 1 oracle oracle 1536 Oct 2 2010 orapworcl -rw-rw---- 1 oracle oracle 1544 May 20 08:16 hc_orcl.dat -rw-r----- 1 oracle oracle 3584 May 20 08:16 spfileorcl.oraThere is no snapshot currently present.
Next, I run a BACKUP CURRENT CONTROLFILE :
[oracle@localhost dbs]$ rman target / Recovery Manager: Release 184.108.40.206.0 - Production on Mon May 20 08:17:53 2013 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-MAY-13 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-MAY-13 channel ORA_DISK_1: finished piece 1 at 20-MAY-13 piece handle=/home/oracle/app/oracle/flash_recovery_area/ORCL/backupset/2013_05_20/o1_mf_ncnnf_TAG20130520T081800_8snhob80_.bkp tag=TAG20130520T081800 comment=NONE channel ORA_DISK_1: backup set complete, elapsed time: 00:00:01 Finished backup at 20-MAY-13 RMAN> quit Recovery Manager complete.
Is there a snapshot controlfile ?
[oracle@localhost dbs]$ ls -ltr|tail -3 -rw-rw---- 1 oracle oracle 1544 May 20 08:16 hc_orcl.dat -rw-r----- 1 oracle oracle 3584 May 20 08:16 spfileorcl.ora -rw-rw---- 1 oracle oracle 9748480 May 20 08:18 snapcf_orcl.f [oracle@localhost dbs]$Yes, a snapshot controlfile did get created !