ORA-15131: block string of file string in diskgroup string could not be read
Cause: A block could not be read because the disk containing the block is either offline or an I/O error occured while reading the block. If this is mirrored file, then all disks that contain a copy of the block are either offline or received errors.
Action: Repair the affected disk and bring it back online. Refer to accompanying error messages to determine which disk has failed.