AlternateUserId (MQCHAR12)

If you specify MQOO_ALTERNATE_USER_AUTHORITY for the MQOPEN call, or MQPMO_ALTERNATE_USER_AUTHORITY for the MQPUT1 call, this field contains an alternative user identifier that is used to check the authorization for the open, in place of the user identifier that the application is currently running under. Some checks, however, are still carried out with the current user identifier (for example, context checks).

If MQOO_ALTERNATE_USER_AUTHORITY or MQPMO_ALTERNATE_USER_AUTHORITY is specified and this field is entirely blank up to the first null character or the end of the field, the open can succeed only if no user authorization is needed to open this object with the options specified.

If neither MQOO_ALTERNATE_USER_AUTHORITY nor MQPMO_ALTERNATE_USER_AUTHORITY is specified, this field is ignored.

• On z/OS, only the first 8 characters of AlternateUserId are used to check the authorization for the open. However, the current user identifier must be authorized to specify this particular alternative user identifier; all 12 characters of the alternative user identifier are used for this check. The user identifier must contain only characters allowed by the external security manager.

  If AlternateUserId is specified for a queue, the value can be used subsequently by the queue manager when messages are put. If the MQPMO_*_CONTEXT options specified on the MQPUT or MQPUT1 call cause the queue manager to generate the identity context information, the queue manager places the AlternateUserId into the UserIdentifier field in the MQMD of the message, in place of the current user identifier.

• In other environments, AlternateUserId is used only for access control checks on the object being opened. If the object is a queue, AlternateUserId does not affect the content of the UserIdentifier field in the MQMD of messages sent using that queue handle.

This is an input field. The length of this field is given by MQ_USER_ID_LENGTH. The initial value of this field is the null string in C, and 12 blank characters in other programming languages.