Hard drives are often used to store sensitive information. To protect this information from unauthorized disclosure, sanitize hard drives prior to reusing, decommissioning, or disposing of them.
Use disk-wiping tools such as the Oracle Solaris format (1M) command to completely erase all data from the disk drive.
Organizations should refer to their data protection policies to determine the most appropriate method to sanitize hard drives.
If required, take advantage of Oracle's Customer Data and Device Retention Service
http://www.oracle.com/us/support/library/data-retention-ds-405152.pdf