HP XP Array Manager Software - Manual (Page 11)

Hardware acceleration: The new storage system channel adapters (CHAs) include hardware
acceleration of Database Validator checksum computation. HP implementation of checksum validation
using hardware acceleration minimizes performance impact (the impact depends on the system
environment).
Multiple levels of checking: In addition to the verification of checksums for overall database blocks,
the storage system also performs checksum validation for lower-level data structures specific to the
type of file. Tablespace and control files have one type of lower-level checking, while redo log files
have another type. Additional lower-level data structure checking increases protection even further.
When Database Validator is turned on using XP RAID Manager, the type of data (data file or redo
log) must be specified so that the correct type of lower-level data structure validation is performed.
Read operations: No additional Oracle checksum validation is completed for read operations. The
Oracle application verifies the checksum at the application end. The storage system performs its own
internal checksum verification on reads and resends the same data that it originally received.
Figure 4 Typical Database System Configuration with Database Validator
Database Validator validates the check data on every write operation to the storage and checks out
the abnormal data immediately after a failure occurs. Database Validator blocks the incorrect write
request from the host, returns a SCSI Check Condition error, and protects the correct data in the
storage. The Oracle database stops itself as an error or separates the damaged table, depending on
the error situation. However, the administrator can recover the database without the loss of data
consistency because any invalid data is not written to the storage, nor is any valid data overwritten.
XP24000/XP20000 Database Validator User's Guide 11