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Syslog message: XMCHIP.*Scheduler: Protect: Parity error for tick table single port SRAM



Article ID: KB31609 KB Last Updated: 06 Oct 2021Version: 3.0

The "Scheduler: Protect: Parity error for tick table single port SRAM" message reports a transient hardware memory error.

This is a Troubleshooting Article for a PFE ASIC Syslog Event.
To view other documented syslog events related to XMCHIP, XLCHIP, MQCHIP, LUCHIP, EACHIP, and PECHIP, see KB31893 - Index of Articles for Troubleshooting PFE ASIC Syslog Events.



When a "Scheduler: Protect: Parity error for tick table single port SRAM" event occurs, a message similar to the following is reported:

Jul 20 11:51:03 router0 fpc7 XMCHIP(0):XMCHIP(0): %-: Scheduler: Protect: Parity error for tick table single port SRAM (2)


  • The error will be reported every second once the condition is triggered.
  • No permanent impact of packet forwarding.
  • Alarm will be raised.
  • There might be service impact in relation to class of service functions.



The cause is due to a transient parity error detected in XMCHIP memory Scheduler block hardware.


Junos OS releases with the fix for PR1083959 automatically corrects this transient memory error. If you still see this syslog event, then automatic recovery has reached a certain threshold.

Perform these steps to determine the cause and resolve the problem (if any).  Continue through each step until the problem is resolved.

  1. Collect the show command output.

    Capture the output to a file (in case you have to open a technical support case). To do this, configure each SSH client/terminal emulator to log your session.

    show log messages
    show log chassisd
    start shell network pfe <fpc#>
    show nvram
    show syslog messages

  2. Analyze the show command output.

    In the 'show log messages', review the events that occurred at or just before the appearance of the "Scheduler: Protect: Parity error for tick table single port SRAM" message. Frequently these events help identify the cause.

  • No RMA required.

  • Restart class-of-service soft during Maintenance Window should clear this error.

  • FPC restart during Maintenance Window should clear this error.

  • With the single occurrence, the alarm can be cleared using command:

    • clear chassis fpc errors fpc-slot <x> all

    • ‚ÄčNote: This command is available in Junos OS 16.1R4-S2, 16.1R5, 16.2R2, 17.1R2, and 17.2R1 or higher.

  • The multiple continuous occurrences of errors require FPC restart during Maintenance Window  window to clear the alarms.

  • Contact JTAC if the issue is seen after FPC restart. 

This article is indexed in KB31893 - Primary Index of Articles for Troubleshooting PFE ASIC Syslog Events; tag XMCHIPTSG

Tip: When looking at an event in the logs, it is important to focus on the first error message in a collection of syslog messages. The first error message is usually the cause of all the follow-on error messages. The follow-on collateral damage error messages can be ignored.


Modification History:
2019-10-14: Article reviewed for accuracy; no changes required.
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