IKJ606I

Explanation
TSO LOGON denied a LOGON request of a user for
one of two reasons: Another user was currently logged on under the same userid.
A member of the installation management staff was using the TSO
ACCOUNT command to alter the authorization of the user to utilize
the TSO subsystem.

System action
The system transmits message IKJ56425I to the
terminal of the user who was unable to log on.

Operator response
None required. If your installation requires
that each individual using the TSO subsystem have his own unique userid,
then the userid of the individual involved may be in use by an unauthorized
individual. If there is any reason to suspect that this is the case,
make sure that the installation manager is informed of the incident.

Source
Time Sharing Option/Extensions (TSO/E)

Routing code
2,9

Descriptor code
6