SET NOCOUNT ON and performance

Sat, 07 Nov 2026 00:00:00 +0000

Co-written with Claude, who ran the testing and research.

TL;DR

Without SET NOCOUNT ON, a procedure that runs 100,000 UPDATE statements in a loop sends 3.9 MB to the client; with it, 75 bytes. These messages go out in full packets, one after the other, without waiting for a reply: so there is no impact on query execution performance. But they cost bandwidth.

The question

A common best practice for stored procedures is to always start them with SET NOCOUNT ON, which stops SQL Server from sending the client, after each statement, the message that gives the number of rows affected (the “(1 row affected)” in SSMS). This message is the DONE_IN_PROC token of the TDS protocol. The SET NOCOUNT documentation says it “can provide a significant performance boost” for procedures that contain loops, because network traffic is greatly reduced. The CREATE PROCEDURE documentation says the opposite: there is no measurable performance benefit on today’s hardware.

Network on Rudi Bruchez

SET NOCOUNT ON and performance

The question