You can create an Oracle ASM Dynamic Volume Manager (Oracle ADVM) volume in a disk group.The volume device associated with the dynamic volume can then be used to host an Oracle ACFS file system.

Example 4–5 Managing volumes with ALTER DISKGROUP VOLUME statements
SQL> ALTER DISKGROUP data ADD VOLUME volume1 SIZE 10G;
Diskgroup altered.

SQL> ALTER DISKGROUP data RESIZE VOLUME volume1 SIZE 15G;
Diskgroup altered.

SQL> ALTER DISKGROUP data DISABLE VOLUME volume1;
Diskgroup altered.

SQL> ALTER DISKGROUP data ENABLE VOLUME volume1;
Diskgroup altered.

SQL> ALTER DISKGROUP ALL DISABLE VOLUME ALL;
Diskgroup altered.

SQL> ALTER DISKGROUP data DROP VOLUME volume1;
Diskgroup altered.

If the volume is hosting an Oracle ACFS file system, then you cannot resize that volume with the SQL ALTER DISKGROUP statement. Instead you must use the acfsutil size command.

1、ACFS

An Oracle ACFS file system is a layer on Oracle ASM and is configured with Oracle ASM storage, as shown in Figure 5–1. Oracle ACFS leverages Oracle ASM 
functionality that enables:
■ Oracle ACFS dynamic file system resizing
■ Maximized performance through direct access to Oracle ASM disk group storage
■ Balanced distribution of Oracle ACFS across Oracle ASM disk group storage for increased I/O parallelism
■ Data reliability through Oracle ASM mirroring protection mechanisms