Fast alter

The database server uses the fast alter algorithm when the ALTER TABLE statement changes attributes of the table but does not affect the data.

The database server uses the fast alter algorithm when you use the ALTER TABLE statement to:
  • Change the next-extent size.
  • Add or drop a constraint.
  • Change the lock mode of the table.
  • Change the unique index attribute without modifying the column type.
  • Add shadow columns for row versioning with the ADD VERCOLS keywords.

With the fast alter algorithm, the database server holds the lock on the table for just a short time. In some cases, the database server locks the system catalog tables only to change the attribute. In either case, the table is unavailable for queries for only a short time.


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