Who needs a license for kdb+?

Everyone. All use of kdb+ is governed by a license.

Commercial versions of kdb+ also need a license key file k4lic to run.

Free, non-commercial, 32-bit kdb+

Use of the free, non-commercial, 32-bit kdb+ distribution, is licenced by the terms and conditions on the download page.

When you start kdb+ you will see on the banner that your license has no expiry date.

KDB+ 3.5 2017.06.15 Copyright (C) 1993-2017 Kx Systems
m32/ 4()core 8192MB sjt mint.local NONEXPIRE

Welcome to kdb+ 32bit edition


Commercial kdb+

If you have a commercial distribution of kdb+, it will abort without a suitable license key file k4.lic. For example, with no license key file:

tom@mb13:~/q$ q
KDB+ 3.5 2017.06.15 Copyright (C) 1993-2017 Kx Systems
m64/ 2()core 8192MB tom mb13.local

Kdb+ signals the error 'k4.lic and aborts.

Obtaining a license key file

Designated Contact

Each Kx customer designates to one technical person as the Designated Contact for issues with kdb+, managing licenses and downloading software.

The banner at the top of the aborted q session above contains machine-configuration information but no license information.

The Designated Contact sends a copy of the banner to to receive a k4.lic license file in return.

Save a copy of k4.lic in the QHOME folder. Restart kdb+ and note the change in the banner.

tom@mb13:~/q$ q
KDB+ 3.5 2017.06.15 Copyright (C) 1993-2017 Kx Systems
m64/ 2()core 8192MB tom mb13.local EXPIRE 2018.05.15 #400
q)til 6
0 1 2 3 4 5

Note the license number (#400 in the example) and quote it in any correspondence about the license.

Keeping the license key file elsewhere

The default location for the license key file is the QHOME folder. You do not have to keep the license there. You can use the environment variable QLIC to specify a different filepath.

Core restrictions

If the license is for fewer cores than the total number on the machine, the number of cores available to kdb+ must be restricted with OS programs, or kdb+ will signal 'cores and abort.

License errors

License questions

Designated Contacts should send license questions to

Emergency failover licenses

In case of an emergency, such as a hardware or infrastructure failure that renders your license key file unusable, the Designated Contact can email to request a temporary failover license to allow use of a different machine or IP address.