DFSMStvs uses the system logger to record log records in log streams. A log stream is a collection of data in log blocks that reside in the coupling facility or on DASD. DFSMStvs uses the system logger because it provides both sysplex-wide logging services and the integrity needed for protected resources. The system logger merges data from multiple instances of an application, including merging data from different systems in a sysplex.