Use the IXGCONN service to connect to or disconnect from a log stream. An application must issue IXGCONN with REQUEST=CONNECT before it can read, write, or delete data in a log stream.
When the IXGCONN REQUEST=CONNECT request completes, it returns a unique connection identifier, called a STREAMTOKEN, to the calling program. The application uses the token in subsequent logger service requests to identify its connection to the log stream.
See z/OS MVS Programming: Assembler Services Guide for more details on connecting to a log stream and log stream tokens.