Alter System Check Datafiles

[Giani]

Hi team list,

What is the purpose of "ALTER SYSTEM CHECK DATAFILES" command and when to use it?
I have tried something like below :

SQL>alter database datafile '/u01/oradata/TBSTEST/test_02.dbf' offline ;

Database altered.

SQL>alter system check datafiles ;

System altered.

So even there is no alert file created from this command.

Your inputs are appreciated

TIA

[nagarjuna]

CHECK DATAFILES
In a distributed database system, such as an Oracle Parallel Server environment,
this clause updates an instance’s SGA from the database control file to reflect
information on all online datafiles.
Your instance should have the database open.
GLOBAL Specify GLOBAL to perform this synchronization for all instances
that have opened the database. This is the default.
LOCAL Specify LOCAL to perform this synchronization only for the local
instance.