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Browse Prior Art Database

Increased Reliability with Redundant Code Background Copy

IP.com Disclosure Number: IPCOM000115624D
Original Publication Date: 1995-Jun-01
Included in the Prior Art Database: 2005-Mar-30
Document File: 2 page(s) / 45K

Publishing Venue

IBM

Related People

Rotter, JS: AUTHOR [+2]

Abstract

A method to maximize the effectiveness of redundant code store via a continuous insurance of code store validity with automatic correction when required is disclosed.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 67% of the total text.

Increased Reliability with Redundant Code Background Copy

      A method to maximize the effectiveness of redundant code store
via a continuous insurance of code store validity with automatic
correction when required is disclosed.

      In this invention, two copies of executable code are
maintained, the active code store and an alternate code store.  This
dual code store allows runtime code updates with no loss of function
by writing to the alternate while executing from the active.  The
redundancy also provides increased reliability if one were to become
damaged.

        To maintain duplicate code in both code stores, they are
periodically tested for correctness by performing a checksum test.
This test can run at Power On Reset, System Power On, System Power
Off, and continuously during normal runtime.  If one becomes damaged,
the good code store is made active and the damaged one (now the
alternate) is rewritten.  This write (Background Copy) is performed
on the mainline and is fully interruptible with no loss of function
or performance.  The test itself is also run in the background
(interruptible) and includes a code level check of the alternate code
store.  If the code level of the alternate does not match the active
code store level a Background Copy to the alternate is also initiated
to make both code stores identical.

      This Background Copy also provides several other services.
Following a code update (write of new code to alternate c...