alter diskgroup check all NoRepair;

check_diskgroup_clause

The check_diskgroup_clause lets you verify the internal consistency of Oracle ASM disk group metadata. The disk group must be mounted. 

Oracle ASM displays summary errors and writes the details of the detected errors in the alert log.

The CHECK keyword performs the following operations:

■ Checks the consistency of the disk.

■ Cross checks all the file extent maps and allocation tables for consistently.

■ Checks that the alias metadata directory and file directory are linked correctly.

■ Checks that the alias directory tree is linked correctly.

■ Checks that Oracle ASM metadata directories do not have unreachable allocated blocks.

REPAIR | NOREPAIR 

This clause lets you instruct Oracle ASM whether or not to attempt to repair any errors found during the consistency check. 

The default is NOREPAIR. The NOREPAIR setting is useful if you want to be alerted to any inconsistencies but do not want Oracle ASM to take any automatic action to resolve them.