Profile chains
In general, these are variables of a profile, which are automatically transferred with this prefix to a called subsequent profile. These variables are therefore only available in the subsequent profile, where they are initialized at the start of Phase 1. See Profile chains. Please also note the special features for the classes CallCronProfile and CallProfile.
See also Metadata editor.
HTTP
However, this prefix is also used for automatically set system variables for HTTP request parameters, HTTP request headers and HTTP Response headers. See HTTP.
AMQP
In addition, such variables can also be used to read parameters in headers of AMQP messages. See AMQP (Input agent).
Reading MSG_CALL_ variables without creating them
See the copy variables into map() function.