I must thank my fellow DBA Franky Weber Faust for his publication in his blog.

In the goal here is to know a bit more about the Flex Disk Group. Let’s see here what a File Group is.

In a Flex Disk Group we can separate our databases, be they PDBs, CDBs or non-CDBs, in different File Group.File Group

Each File Group belongs to one, and only one, Disk Group.

To demonstrate some examples we will re-create the PDB pdb1 only in Disk Group FLEX:

I now consult to see where the PDB1 PDB files were created:

Let’s create a File Group, but first let’s look at the current situation of Disk Group FLEX:

Notice that there is already a File Group DEFAULT_FILEGROUP and another with the same name as our PDB: PDB1.

I’ll create another PDB to verify the behavior:

We confirm that the PDB pdb2 is stored entirely in Disk Group FLEX:

Again check the existing File Groups:

I hereby confirm that for each created PDB, a File Group with the same name is also created.

Now let’s see how to create a new File Group. For this we perform the following command in SQL*Plus of the ASM instance:

Notice that I gave the File Group name and also the database that will be stored in it.

Let’s see how it got now:

Notice that when you try to remove the File Group PDB1 there is an error stating that there are files inside it:

So let’s do the following … I’ll create a new File Group and then a new PDB and then store it in this File Group:

Now I will create the PDB pdb3:

Notice that this time the created PDB was stored correctly in the desired File Group and ASM did not create a default File Group with the name of the PDB:

In conclusion … If you want to use Flex Disk Groups, be sure to first create the File Group and then create your databases.

I did some testing moving datafiles from one Disk Group to another, but until then I have not figured out if there is a way to move an ASM File to another File Group. The documentation regarding the Flex Disk Group is still very precarious.

I’ll do some more articles about this feature of Oracle 12cR2, so stay tuned.

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