All language subtitles for [SubtitleTools.com] RMAN Complete Recovery - Learning Oracle 12c [Video]

In this lesson, we're going
to discuss complete recoveries

with RMAN.

Now, a complete
recovery is going

to be a recovery where all
the data is recovered up

to the point of failure.

So what we're going
to do in this example

is actually simulate a failure
and perform a recovery.

So it goes without saying that
in order to perform a recovery,

we must have a good backup.

So we ensure that we have a
good backup before we attempt

to simulate a media failure.

We need to remember that
when we do a recovery,

it must be done in
the mount state.

So the database
must be in mount.

We cannot do a database recovery
while the database is in no

mount state or in open state.

And indeed, if we
have a media failure,

it's not very likely
that the database

would be in an open state, at
least in any functional way.

When we do complete
recoveries, we

can do them much in the
same way as backups.

So we can do them at the
tablespace level, the data file

level, or the entire database.

And recovery
involves two steps--

restore and recover.

Restore is restoring the
backup, the file from a backup.

And recover is the act of
rolling it forward, applying

all the changes that have
occurred that are in the redo

logs and archive logs.

So restore and recover.

So in order to simulate
this, log into RMAN.

Connect target.

And shut down the database.

In this case, we need to
shut down the database

because Windows will
prevent us from actually

doing what I'm about to do.

That is to change the name on a
data file simulating its loss,

because it locks the files
when the database is open.

However, on Linux
and Unix, you are

free to go and destroy
a file, one of the data

files of the database, without
the operating system stopping

you.

The database is shut down.

And so I'm going to go
to the directory that

holds the data files.

Oracle Base
directory, there'll be

an oradata, the name of the
database, and then data file.

And so I'm going to target
the data file that belongs

to the user's tablespace.

And just for slight
safety's sake,

I'm just going to rename
this, rather than delete it,

to dot old.

However, the effect is
the same, because when

the database
attempts to start, it

will have a problem because it
will not find this data file

that it expects to be there.

The data file locations are
written in the control file,

and it expects all of
those to be there when

the database startup occurs.

I'm going to exit out of here.

sqlplus as sysdba.

And now, we're going
to just type startup

and see how far we get.

So notice that the instance
started and gave us

the information
about the memory.

And the database made
it to mount state.

But it couldn't get
any farther than that.

It says I cannot identify
our locked data file number 4

and then gives us that file.

And there it is, the
data file that belongs

to the user's tablespace.

And so it cannot see it, so
it's as if we just went ahead

and deleted it.

So now, we are already
in the mount state,

so we're in a position that
we can restore and recover

this data file.

So we say restore data file 4.

And that, again, is the
number of the data file

that's indicating is missing.

And we need to be
in RMAN to do this.

The RMAN connect target,
restore data file 4.

So what it's doing right
now is reading the backed up

data for data file
number 4 from our backup,

and its restoring it.

And if we were to
see, notice that it

has restored a data file
for the user's tablespace.

But we're not
finished, because we

would need to recover
all of the data that

was lost between the time that
the database was shut down

and when the data file was lost.

So we say recover data file 4.

Starting media recovery.

Media recovery complete.

And now, our database
is ready to be opened.

So we do alter database open.

So what would we do in the
event of a complete loss

of the database?

So what if we lost all of the
data files in the database

if I'd actually just remove
those files that are here

under the data file directory?

Well, the process would
be very, very similar.

We would simply type restore
database and then recover

database.

And following the
activity that occurred,

our database would be fully
recovered and restored.