Re: Backup and Recovery and DR - RMAN vs. NOT

I Agree with you as long as it is Rman towards tape not toward disk. I love Rman direct to tape as I hate Rman to disk. There is a world between Rman to disk and Rman to tape.  

 So let's consider what happen in the case where the catalog is not connect to a media tape layers and what is handy feature is left of Rman :    

 rman << EOF

    connect target / ;
    connect catalog mycat/*****@cat.db -- Determining the right credentials was the *hardest* part!     restore database ;
    recover database ;
    open database ;
 EOF    

1. connect target / : This assume that you have retrieved a good controlfile for this backup. Since it is backup on disk, you somehow provided it yourself.
2. connect catalog : no special comment
3. restore database : You had to provide the set of correct dataset files. You got the list from catalog. Problem is that you needed to dump from tape this dataset into a staging area, and after that Rman will read them and recreated the datafiles ===> twice the disk space and twice the IO, and all that providing you retrieve the correct set of datasets file whose name is a pure garbage.
4. recover database : again you dumped from tape the correct dataset of files containing all requested archive logs. good news is that this time you won't need twice the disk space. bads news is you need to check manually with the command 'list achive all' which dataset contains which archives and bring them all from tape.
5. open database ; just a shorter way to type 'alter database open [resetlogs]'

 So what did you gain in fact.? Rman, when not to tape leaves you with all the fuss to providd the files yourselves and requires twice the space to restore a datafile.  

 B. Polarski
 http://www.smenu.org

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