VMWare ESX 6 Change Block Tracking (CBT) corruption

Solution In Progress - Updated -


  • VMWare ESX 6
    • Virtual machine backup
    • Virtual machine Power on
    • Expanding the size of the virtual disk
    • Taking virtual machine quiesced snapshots
  • Red Hat Enterprise Linux 5, 6, 7
  • Backup software using Change Block Tracking (CBT)
  • Oracle DB 11.X, 12.X
  • Any file system


  • DB files getting corrupted frequently
  • File system corruptions


Root Cause

Known issues

Diagnostic Steps

  • Oracle error messages like:
ORA-00742: Log read detects lost write in thread 1 sequence 92 block 30215
  • Per VMWare KB note
You can observe error log similar to the following in the /var/log/vmkernel.log file:
<YYYY-MM-DD>T<TIME>.nnnn cpu5:nnnnnn)WARNING: CBT: 191: No memory available! Called from 0xnnnnnnnnnnnn

The vSphere Client might display an error message similar to the following when you attempt quiesced snapshot:
An error occurred while taking a snapshot: msg.snapshot.error-QUIESCINGERROR

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