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HP OpenVMS Systemsask the wizard |
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The Question is: I have always beleived that OpenVMS PID's are unique for as long as the system is booted and are only re-used after a reboot. Is this true? And if so, is there any limit to PID's - i.e. the 8 hex digits normally displayed? What would happen if this lim it were reached? I know 8 billion unique processes should be enough for anyone and we are not in imminent danger of hitting this limit, but I would still be interested in the 'what if' scenario, particularly as a few UNIX-types are siting this as a weakness with OpenVMS The Answer is : With OpenVMS, the PID format (both external and internal PID varieties in the current model) formats are undocumented and subject to change without notice. The current format of the external and internal PIDs are listed in the OpenVMS Internals and Data Structures Manual (IDSM), though the OpenVMS Wizard strongly discourages any dependencies on PID format be implemented in any application software. As for what happens when the PID itself wraps, well, nothing particularly interesting happens. The value wraps. Continous OpenVMS system uptimes of fifteen or more years are known to have occured on customer systems, so there is some experience with very extended system uptimes. With the wrapping of the PID, you will have the potential for duplicate PIDs in accounting and auditing files, particularly if you have not recreated new versions of the accounting and auditing logs during the intervening years. That said, due to the construction of the PID, you cannot and will not have duplicate PIDs active on the same system or same cluster at the same time. Also due to the construction of the PID, a very long time will transpire between any particular uses of any particular PID value. UNIX has a very similar process identification (PID) construct.
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