Reference Guide

1092 | E-Series TeraScale Debugging and Diagnostics
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Parity error detection and correction
There are two types of parity errors: transient and real.
• Transient Parity Error— implies that a read value was corrupted in transit but that the actual
memory may not be corrupt. Transient errors are further categorized as a recoverable and phantom.
• Recoverable Transient Parity Error—a transient parity error indicated by SRAM that FTOS
was able to correct (rewrite).
• Phantom Transient Parity Error—a recoverable parity error for which the software was unable
to determine a problem location.
• Non-recoverable Error—implies a persistent corrupted memory location for which the only means of
recovery is to reboot the line card.
FTOS has the ability determine the error type when a parity error occurs and correct recoverable transient
parity errors using the Parity Error Correction feature. During the SRAM scanning function, anytime the
system detects a parity error, it must determine which type it is. To distinguish between the two types of
parity errors (transient and non-recoverable), the system maintains a copy of all SRAM writes. If a location
does not match the SRAM copy or causes another parity error indication in the status register, the system
rewrites the location. After rewriting the location, the system again reads the location and checks the status
register for parity error indication. If the location fails either of these two tests after a rewrite, then the
parity error is non-recoverable, the location is marked as corrupt, and FTOS generates log messages. If the
location passes these tests, then the parity error is transient (recoverable), the location is marked as having
had a transient parity error, and FTOS continues the scan to the end of the SRAM bank.
Enable parity error correction
Parity Error Correction is disabled by default and consumes 25 megabytes of line card memory when you
you enable it.
To enable Parity Error Correction:
FTOS displays Message 8 on the console, when you enable Parity Error Correction. FTOS also records the
messages in Message 9 in the trace log when you enable and disable Parity Error Correction, or insert a
line card with Parity Error Correction enabled.
Step Task Command Command Mode
1 Verify that the line card has sufficient memory
to enable this feature, as shown in the example
below.
show processes memory lp EXEC Privilege
2 Enable Parity Error Correction hardware monitor linecard asic fpc
parity-correction
CONFIGURATION
3 Reload the linecard. reset linecard EXEC Privilege