Which is the default error handler available in OSB?

OSB provides a System Error Handler that is globally available across all services and pipelines by default. This system-level handler catches unhandled errors that propagate up through the execution stack. Service-level error handlers must be explicitly configured within a specific service. Pipeline pair level handlers are attached to specific pipeline pairs. Stage-level handlers operate within a single stage. The system-level handler is the only one that exists by default without explicit configuration, providing a safety net for all errors.