DBCC TRACEOFF 3604

Question

DBCC TRACEOFF 3604

Urantia 0

Good afternoon

SQL 2022 Standard

I would like to better understand:

DBCC TRACEOFF 3604
DBCC TRACEON 3604

How to use it?

How to activate it?

How and when should it normally be used?

Thank you

Urantia

2 answers

Your answer

Answer 1

Erland Sommarskog 128.6K MVP Volunteer Moderator

For some DBCC commands, output is only written to the SQL Server errorlog by default. If you also want the output in SSMS, you need to enable TF 3604.

I'm not sure in which DBCC commands this applies to. It may be a thing of the past, so that there are no such DBCC commands any more - at least not documented once. I cannot recall having seen any reference to TF3604 for a long time.

Urantia 0 Reputation points

2025-11-18T17:57:03.7633333+00:00
Hello Erland

Given this scenario:

SQL Server 2022 is installed on server A.

Is not allowed remote access from outside the company to this server.

While I am at home, I access the company's network via a VPN and run SSMS (installed on my home PC), and through it I access the SQL Server A.

If I enable DBCC TRACEON 3604:

the output is written only in SSMS on my PC?

Is also written to the SQL Server A logs?

Thank you in advanced

Urantia
Erland Sommarskog 128.6K Reputation points MVP Volunteer Moderator

2025-11-18T18:05:27.6566667+00:00

Whether you are connected over VPN or not has no importance. The result will be the same.

Furthermore, TF 3604 only applies to specific DBCC commands. Normally, you would have no reason to use it.
Urantia 0 Reputation points

2025-11-18T19:39:44.06+00:00
you say:

Whether you are connected over VPN or not has no importance. The result will be the same.

--- The result is:

the output is written only in SSMS on my PC or is also writen to the logs os SQL?

Furthermore, TF 3604 only applies to specific DBCC commands. Normally, you would have no reason to use it.

--- I am analising why someone does it.

Thanks
Erland Sommarskog 128.6K Reputation points MVP Volunteer Moderator

2025-11-18T19:48:27.1333333+00:00
Whether you are connected over VPN or not has no importance. The result will be the same. --- The result is:

the output is written only in SSMS on my PC or is also writen to the logs os SQL?

What I'm saying is that VPN or nor have no bearing to behaviour controlled by TF3604.

So if a command writes to the SQL Server errorlog only, it will write to the errorlog only, no matter you are on VPN or nor.

If a command writes to the errorlog by default, but output to SSMS can be enabled by TF 3604, it will do so, VPN or not.

If you enable TF 3604, such a command will write both to the errorlog and to SSMS, no matter you are on VPN or not.

Normal results and error messages are never written to the errorlog, only in SSMS. And again, VPN or not has nothing to do with it.

--- I am analising why someone does it.

You have a user who enables TF3604 and you want to know why. Why don't ask that user?
Urantia 0 Reputation points

2025-11-18T21:04:53.9233333+00:00

Erland Sommarskog

It's a internal question.

But I understand now. Thank you for the clarification.

Best Regards

Answer 2

DBCC TRACEOFF 3604: This command is used to disable the trace flag 3604. When trace flag 3604 is enabled, it allows the output of certain DBCC commands to be printed to the console, which can be useful for debugging and monitoring purposes. Disabling it with DBCC TRACEOFF 3604 will stop this output.
DBCC TRACEON 3604: This command enables trace flag 3604, allowing the output of DBCC commands to be displayed in the console. This is particularly useful when you want to see detailed information about the execution of certain commands, such as DBCC PAGE or DBCC CHECKDB.

How to Use It:

To activate trace flag 3604, you would run the following command in your SQL Server Management Studio (SSMS):
```
  DBCC TRACEON(3604);
```
To deactivate it, you would run:
```
  DBCC TRACEOFF(3604);
```

When to Use It:

DBCC TRACEON 3604 is typically used when you are troubleshooting or debugging issues in SQL Server. It can provide valuable insights during the execution of certain DBCC commands, helping you understand what is happening internally.
DBCC TRACEOFF 3604 should be used after you have gathered the necessary information and no longer need the detailed output to avoid cluttering the console with unnecessary messages.

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DBCC TRACEOFF 3604

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