Files should be equally balanced across all disks. The following queries and script can be used to check disk group balance:

• To check I/O balance, query the V$ASM_DISK_IOSTAT view before and after running a large SQL statement. For example, if a large query has a lot of reads, then the values in the read column and the read_bytes column should be approximately the same for all disks in the disk group.

• To check all mounted disk groups, run the script available in My Oracle Support document 367445.1.