System Management and Startup/Shutdown
Day-to-day system management centers on SYSMAN, SYSGEN, and the startup/shutdown command procedures. SYSMAN provides environment-based management (SET ENVIRONMENT) and commands such as CONFIGURATION SHOW, DO (execute a DCL command across nodes), and SET PASSWORD/SET TIMEOUT for security settings. SYSGEN reads and writes the system parameter file and can change parameters for the running system (dynamic) or for the next boot (with WRITE CURRENT). Know that not all parameters are dynamic - some require a reboot.
Startup is layered: the system startup procedure calls site-specific and layered product startup files. Understand that site-specific customizations belong in SYLOGICALS.COM, SYSTARTUP_VMS.COM, and SYCONFIG.COM rather than editing vendor files; a classic trap is placing customizations in a file that gets overwritten on upgrade. Shutdown should be graceful: use @SYS$SYSTEM:SHUTDOWN to stop the queue manager, dismount volumes, and halt or reboot cleanly. Abrupt power loss risks file-system inconsistency.
Traps: confusing SYSMAN's SET ENVIRONMENT with changing the process default directory; assuming SYSGEN changes take effect immediately (only dynamic ones do); and forgetting that OPER privilege or BYPASS is needed for many management operations. Also know how to check the system with SHOW SYSTEM, SHOW USERS, and MONITOR, and that accounting and operator logging (OPCOM) are part of management.
Rule of thumb: if a parameter change must survive a reboot, use SYSGEN ... /WRITE (or WRITE CURRENT) and verify with SHOW; if it must apply now, confirm it is dynamic.