Subject Re: [firebird-support] UPDATE to same record causing heavy disk I/O
Author Ann Harrison
On Wed, Dec 23, 2015 at 7:12 AM, Alexey Kovyazin ak@... [firebird-support] <> wrote:

longest chain of versions here).

If you will see a long chain of versions, it means that you are updating the same record while some other writeable transaction is active, or some old transaction was rollabacked with mark on TIP, so it makes Firebird to preserve versions of updated record.

Updating a record will always create a back version, even if there are no other users in the database.  Back versions function in three ways:  

  1) They provide a non-blocking consistent view of data for concurrent transactions.
  2) They allow Firebird to detect and prevent conflicting updates.
  3) They are the mechanism for verb, savepoint, and transaction rollback

The third function must be available even in single user applications.  

Good luck,