16.20 - Write MI to Disk for Faster Startups - Teradata Database - Teradata Vantage NewSQL Engine

Teradata Vantageā„¢ NewSQL Engine Release Summary

Teradata Database
Teradata Vantage NewSQL Engine
Release Number
March 2019
Content Type
Release Notes
Publication ID
English (United States)
Last Update

A duplicate (snapshot) copy of the file system master index (MI) is kept in memory and periodically written to disk. On system restart, Teradata Database can reconstitute the MI by reading the latest disk copy, rather constructing the MI by reading cylinder indexes (CIs) on each AMP.

The Ferret and Filer utility SCANDISK command has been enhanced to check the validity of the snapshot MI.

A new SNAPMI command has been added to the Filer disk utility that allows you to
  • Display the snapshot MI, including the disk location(s) for which the MI was last written
  • Validate the structure of the snapshot MI
  • Invalidate the snapshot MI to prevent it from being used at the next system restart or Filer invocation


  • Speeds most system restarts by eliminating time-consuming step of rebuilding the MI from scratch.
  • Similarly, this feature can speed up starting the Filer utility when the database is down or when Filer is started on a FATAL AMP. Filer uses the MI, and having a snapshot to use means Filer often does not need to rebuild the MI.
  • Two copies of the snapshot MI are written to disk for redundancy.


  • Minor performance impact from periodic writing of MI to disk.

Additional Information

For more information on MI snapshots, see Filer in Support Utilities , B035-1180 .