Shutting Down UOS

Most things have their counterpart, especially when it comes to computers. As LOGIN has the corresponding LOGOUT, so system startup has system shutdown. Obviously, one could simply power a computer off, but that leaves the disk(s) dirty, which requires them to be cleaned during startup (a slower process than simply shutting things down properly). But there are also issues with shutting down queues, handling clusters, letting applications shut down in an orderly fashion, and - on multiuser systems - giving users a little advance notice. This is the purpose of the SHUTDOWN script in sys$system. Here is the documentation (intended for system administrators) for shutdown and for the OPCCRASH utility.

SHUTDOWN
Shut down the system

Format:
SHUTDOWN {option}

option

One of the following options may be specified to modify the behavior of shutdown. These options are provided for the sake of single-user systems and should not be used with multi-user systems or systems in clusters. When used, it is equivalent to answering the defaults to all the questions normally asked, except for "should an automatic system restart be performed".

Option	Description
POWER_OFF	Immediate shutdown and power-off the system.
REBOOT	Immediate shutdown and reboot.
HIBERNATE	Hibernate the system and power down.

The shutdown script performs an orderly system shutdown. If no options are specified, it will ask some questions, as follows:

How many minutes until final shutdown [0]:
Provide the number of minutes to wait until the system shuts down. If users are logged-in, it is usually a good idea to give about 5 minutes notice. However, in an emergency, you can specify 0 to initiate an immediate shutdown.

Reason for shutdown [Standalone]:
Enter a short message to indicate to users the reason for the shutdown. If this is a single-user system, pressing ENTER will provide no reason messages.

Do you want to spin down the disk volumes [No]?
If you are using external disk drives, this indicates whether or not they should be spun down. It has no effect on internal or network drives. If the external drives are dual-ported and connected to other systems, they should not be spun down or the other systems will not be able to access them.

Do you want to invoke the site-specific shutdown script [Yes]?
If you wish to run the site-specific shutdown script, press ENTER or enter "Yes". Otherwise enter "No" and the site-specific shutdown script will not be run.

Should an automatic system restart be performed [No]?
If you answer "Yes", the system will restart after shutting down. If you enter "No" or press ENTER, the system will power down after shutdown.

When will the system be rebooted [later]?
Here you can enter a message about when the system will be restarted. This us for the benefit of any logged-in users. If you press ENTER, the message will be that the system will be rebooted "later".

Shutdown options [NONE]:
Here you may enter zero, one, or multiple options for shutdown. If you enter more than one, separate them with commas. This script will list the valid options before prompting you. The following options are valid:

REMOVE_NODE	Remaining nodes in a cluster should decrement the EXPECTED_VOTES system parameter. However this will not decrease the EXPETED_VOTES below the quorum value. This will also dismount all locally attached disks clusterwide, which may affect applications running on other nodes. Use this option if the node you are shutting down will be out of the cluster for an extended period of time. This option has no effect if this system is not part of a cluster.
CLUSTER_SHUTDOWN	Entire cluster is being shut down. This does not shutdown any other nodes in the cluster. It simply indicates that this system's shutdown is part of a cluster shutdown and is used to synchronize the shutdown of the cluster. This option must be used on each node during shutdown. Only when shutdown has reached a certain point on all nodes will the nodes all complete shutdown.
REBOOT_CHECK	Verify that the system is bootable. If there is no boot information on the disk, the shutdown will be cancelled.
SAVE_FEEDBACK	Save usage characterists for this boot session. This can be used later for system tuning.
DISABLE_AUTOSTART=n	Disable auto-start queues in n minutes. Although no additional jobs will autostart while system shutdown is happening, this gives the queues time to finish their current jobs before the system shuts down. However, any jobs running when the number of minutes is past will be stopped or failed over to another node on the cluster.

At this point, the system shutdown will begin. The process follows these steps:

1. The system symbol shutdown$time is set to the absolute time of the shutdown. This symbol can be checked at any time to see if the system is being shutdown and when that shutdown is scheduled.
2. At various intervals, a message is broadcast to all users on the system requesting them to log off.
3. If the DISABLE_AUTOSTART option was specified, at the time indicated all autostart jobs are terminated or failed-over.
4. At 6 minutes, or less, before shutdown, the terminal running shutdown will become an operator console. All users connected through SET HOST will lose their connection. The network is shut down. All further non-operator logins are disabled.
5. One minute, or less, before shutdown, all queue jobs are terminated (or failed over) and the queue manager is stopped.
6. At the time of shutdown, the site-specific shutdown script is started, unless otherwise specified.
7. All remaining user processes are stopped.
8. On multiprocessor systems, all secondary processors are stopped.
9. All installed images are removed.
10. All mounted file systems are dismounted except for the boot disk. If requested, all external drives are spun down, nor are quorum disks spun down.
11. The operator log file is closed.
12. sys$system:OPCCRASH.EXE is run to shutdown the system.
13. If a restart was requested, the system reboots.

System symbols can be defined that will affect the operation of the shutdown script as follows. The default indicates what value is used if the symbol is not defined.

Symbol name	Default	Description
shutdown$net_minutes	6	Number of minutes before shutdown when the network is shut down.
shutdown$disable_autostart	1	Defines the number of minutes before shutdown when the autostart queues are disabled.
shutdown$inform_nodes		A comma-delimited list of all nodes to notify about the shutdown.
shutdown$minimum_minutes	0	The minimum number of minutes that can be given before shutdown. You will not be able to specify a value less than this when prompted by the shutdown script.
shutdown$queue_minutes	1	The number of minutes before shutdown when queues are shut down.
shutdown$time		Defined by the shutdown script to indicate the absolute time of the shutdown.
shutdown$verbose		If any non-null value, the shutdown script will list each disk as it is dismounted.

Example:

$ @SYS$SYSTEM:SHUTDOWN
         SHUTDOWN -- Perform an Orderly System Shutdown
 
How many minutes until final shutdown [0]: 10
Reason for shutdown: [Standalone] SYSTEM UPGRADE
Do you want to spin down the disk volumes [No]?
Do you want to invoke the site-specific shutdown procedure [Yes]?
Should an automatic system reboot be performed [No]?
When will the system be rebooted [later]?
Shutdown options (enter as a comma-separated list): 
 REMOVE_NODE         Remaining nodes in the cluster should adjust quorum 
 CLUSTER_SHUTDOWN    Entire cluster is shutting down 
 REBOOT_CHECK        Check existence of basic system files 
 SAVE_FEEDBACK       Save performance feedback information from this boot 
 DISABLE_AUTOSTART   Disable autostart queues
Shutdown options [NONE]: 
SHUTDOWN message on MYCOMPUTER, from user SYSTEM at _MYCOMPUTER$TERMA0:  14:00:00.00
MYCOMPUTER will shut down in 10 minutes for SYSTEM UPGRADE; back up later. Please log off 
node MYCOMPUTER.
%SHUTDOWN-I-OPERATOR, This terminal is now an operator's console.
%%%%%%%%%%%  OPCOM, 11-DEC-2023 14:01:00.10  %%%%%%%%%%%
Operator status for operator _MYSYSTEM$TERMA0:
PRINTER, TAPES, DISKS, DEVICES, NETWORK, OPER1
%SHUTDOWN-I-DISLOGINS, Interactive logins will now be disabled.
%SET-I-INTSET, login interactive limit = 0 current interactive value = 1
%SHUTDOWN-I-SHUTNET, The network will now be shut down.
 
SHUTDOWN message on MYCOMPUTER, from user SYSTEM at _MYCOMPUTER$OPA0:   14:05:00.30
MYCOMPUTER will shut down in 5 minutes for SYSTEM UPGRADE; back up later. Please log off 
node MYCOMPUTER.
2 terminals have been notified on MYCOMPUTER.
SHUTDOWN message on MYCOMPUTER from user SYSTEM at _MYCOMPUTER$TERMA0:   14:06:50.31
MYCOMPUTER will shut down in 3 minutes for SYSTEM UPGRADE; back up later. Please log off 
node MYCOMPUTER.
%%%%%%%%%%%  OPCOM, 11-DEC-2023 14:07:12.30  %%%%%%%%%%%
SHUTDOWN message on MYCOMPUTER user SYSTEM at _MYCOMPUTER$TERMA0:   14:08:12.40
MYCOMPUTER will shut down in 2 minutes for SYSTEM UPGRADE; back up later. Please log off 
node MYCOMPUTER.
%%%%%%%%%%%  OPCOM, 11-DEC-2023 14:08:11:50  %%%%%%%%%%%
Message from user SYSTEM on MYCOMPUTER 
-SYSTEM-S-NORMAL, normal successful completion
%%%%%%%%%%%  OPCOM, 11-DEC-2023 14:08:42.30  %%%%%%%%%%%
%SYSTEM-I-STOPQUEUES, The queues on this node will now be stopped.
SHUTDOWN message on MYCOMPUTER from user SYSTEM at _MYCOMPUTER$OPA0:   14:09:12.56
MYCOMPUTER will shut down in 1 minute for SYSTEM UPGRADE; back up later. Please log off 
node MYCOMPUTER.
SHUTDOWN message on MYCOMPUTER, from user SYSTEM at _MYCOMPUTER$TERMA0:   14:10:00.20
MYCOMPUTER will shut down in 0 minutes for SYSTEM UPGRADE; back up later. Please log off 
node MYCOMPUTER.
17 terminals have been notified on MYCOMPUTER
%SHUTDOWN-I-SITESHUT, The site-specific shutdown procedure will now be invoked.
%SHUTDOWN-I-STOPUSER, All user processes will now be stopped.
%SHUTDOWN-I-REMOVE, All installed images will now be removed.
%SHUTDOWN-I-DISMOUNT, All volumes will now be dismounted.
%%%%%%%%%%%  OPCOM, 11-DEC-2023 14:09:42.30  %%%%%%%%%%%
Message from user System on MYCOMPUTER 
_MYCOMPUTER$TERMA0:, MYCOMPUTER shutdown was requested by the operator.
%%%%%%%%%%%  OPCOM, 11-DEC-2023 14:10:02.44  %%%%%%%%%%%
Logfile was closed by operator _MYCOMPUTER$TERMA0: 
Logfile was SYS$SYSROOT:[SYSMGR]OPERATOR.LOG
%%%%%%%%%%%  OPCOM, 11-DEC-2002 14:10:32.20  %%%%%%%%%%%
Operator _MYCOMPUTER$TERMA0: has been disabled, username SYSTEM
        SYSTEM SHUTDOWN COMPLETE

OPCCRASH
Force system shutdown

Format:

OPCCRASH {/NODUMP}{/RESTART}

The shutdown script should be used to shut down the system. OPCCRASH should only be used if the shutdown script doesn't work. The CMKRNL privilege is necessary to run OPCCRASH.

OPCCRASH performs the following procedures:

1. All processes other than the one running OPCCRASH are immediately terminated.
2. Any modified memory pages are written out to the disk.
3. Write a crash dump, unless /NODUMP specified or the opc$nodump system symbol is defined and non-null.
4. Dismount boot disk.
5. Either power off the system or restart (if /RESTART was specified).

In the next article, we will look at the shutdown script.