Oracle Error Message
ORA-15131: block string of file string in diskgroup string could not be read
Reason for the Error
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.
Solution
Repair the affected disk and bring it back online. Refer to accompanying error messages to determine which disk has failed.