Skip to content


Who needs a license for kdb+?

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

Licenses at

64-bit versions of kdb+ also need a license key file (k4lic, or kc.lic for kdb+ on demand) to run.

Free, non-commercial, 64-bit kdb+ on demand

kdb+ on demand 64-bit personal edition is for personal, non-commercial use. It may be used freely on up to 2 computers, and up to a maximum of 16 cores per computer, but is not licensed for use on any cloud – only personal computers. It may not be used for any commercial purposes.

kdb+ on demand requires an always-on internet connection to operate.

Free, non-commercial, 32-bit kdb+

Use of the free, non-commercial, 32-bit kdb+ distribution, is licensed 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 64-bit kdb+

Use of commercial 64-bit kdb+ is licensed by your agreement with Kx.

License key files

32-bit kdb+

The 32-bit kdb+ distribution does not require a license key file.

64-bit kdb+

64-bit distributions of kdb+ (commercial and personal) require a valid license key file. Without one, kdb+ signals an error 'k4.lic and aborts.

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

The license key file is k4.lic, or kc.lic for kdb+ on demand. If both are found, the kc.lic file is used.

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 license file in return.

Save a copy of the license file 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.

Folder not file

Like QHOME, QLIC points to a folder, not a file. For example,

$ QLIC='/Users/simon/q'

Licensing server for kdb+ on demand

As well as a license key file, kdb+ on demand also requires frequent contact with the licensing server. For this you need an always-on Net connection.

If kdb+ cannot contact the server it will abort with a timestamped message.

'2018.03.28T11:20:03.831 couldn't connect to license daemon -- exiting

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.

As long as you task or numa correctly, the binary will not abort itself.

You can see the number of cores entitled to a q process:

  • by looking at the banner, e.g. …w64/ 2(16)core… – the 2 here is what the process is allowed to use, and the 16 is the licensed amount
  • with .z.c – not the physical cores of the system, but rather the number the process is allowed to use
  • the first element of .z.l

The number of licensed cores is always 16 for the on-demand license.

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.