Fast Rebalance in ORACLE11g

SQL> SELECT name FROM v$asm_diskgroup;
NAME ------------------------------ DATA
SQL> ALTER DISKGROUP data DISMOUNT;
Diskgroup altered.
SQL> ALTER DISKGROUP data MOUNT RESTRICTED;
Diskgroup altered.
SQL> ALTER DISKGROUP data DISMOUNT;
Diskgroup altered.
SQL> ALTER DISKGROUP data MOUNT;
Diskgroup altered.
SQL> In a RAC environment, a disk group mounted in RESTRICTED mode can only be accessed by a single instance.
The restricted disk group is not available to any ASM clients, even on the node where it is mounted.
Using RESTRICTED mode improves the performance of rebalance operations in a RAC environment as it elimitates the need for lock and unlock extent map messaging that occurs between ASM instances.
Once the rebalance operation is complete, the disk group should be dismounted then mounted in NORMAL mode (the default).