HP XP Array Manager Software - Manual (Page 10)

very robust data protection capabilities that can prevent data corruption within both DBMS and the
storage system, but until now, they could not detect data corruption that occurred between DBMS
and the storage system.
The other data corruption risk is a non-Oracle application overwriting the Oracle data files on the
storage system. The Database Validator function also protects existing Oracle data files from being
overwritten by data from other applications.
Figure 3 Typical Database System Configuration
Overview of Oracle HARD and Database Validator Operations
Figure 4 shows a typical system configuration with Database Validator. The Oracle Hardware Assisted
Resilient Data (HARD) feature protects against data corruption. The Oracle application software
computes checksums which are included with every data block written to disk. The Database Validator
feature recomputes the checksums upon receiving data blocks that are written to Oracle database
volumes. In the event that the HP storage system receives a corrupt block, the I/O operation is rejected
with a checksum failure error. The storage system recognizes that it has received corrupt data and
rejects the I/O. This prevents corrupt data from being written to the database and eliminates silent
data corruption. Without Database Validator (but with Oracle HARD), corrupt data is discovered, but
only when the data is read back at a later date.
HP storage systems already perform extensive checksum-type validation of data integrity from the
point of entry and throughout the entire storage system. The new Database Validator feature detects
corruption occurring outside the storage system by checking write data upon receipt. The objective
is to prevent corrupt data destined for Oracle volumes from being accepted by the storage system.
Detection of corrupt data: If the Database Validator function detects corrupt data, the I/O operation
from the host is rejected, as if there had been a hardware failure. The error code indicates “HARD
failure.” If the data corruption problem is transient, the condition may clear when the host retries the
I/O. If there is no successful retry operation, the application I/O operation fails, and the Oracle
update transaction does not complete.
About Database Validator Operations 10