Technical data

Setting System Time
6.9 Using SYSMAN to Manage System Time
In an OpenVMS Cluster system (or for a node that is not part of the cluster),
when you set the time, the TODR and the base time in the system image are
reset with the values for the new year. However, multiple systems might share
the system image. This does not normally cause a problem except after the first
day of a new year.
Note
The system issues the SET TIME command when it boots and as a part
of the normal SHUTDOWN command procedure.
By December, each node has a very large offset stored in the TODR (from the
base time of 1-JAN of that year). When the time advances to a new year, the
system image still has the old year and the TODR values are still large.
After January 1, if a SET TIME command is issued on any node (or any node is
shut down using SHUTDOWN.COM), the following events occur:
1. The new year becomes the base year.
2. The system resets the TODR on that node.
3. The other nodes still have a large value in the TODR.
After these three events occur, if a node that has a large TODR crashes and
rejoins the cluster, its system time is initially in the next year (applying the
large TODR to the new year). This system time is recorded as the system’s boot
time. When the node joins the cluster, its time is set to the correct value but the
boot time remains one year in the future. Certain forms of the SHOW SYSTEM
command compare current time to boot time; in this instance, SHOW SYSTEM
displays incorrect values.
If a system disk is used at different times by different, unclustered CPUs or if
different system disks are used at different times on the same CPU, the system
might incorrectly set the time to a year in the future or a year in the past,
depending on how the CPU’s TODR and the value recorded on the system disk
become unsynchronized:
• Sharing a system disk across multiple CPUs pushes the time into the future
• Using multiple disks on one CPU pushes the time into the past
Example
The following example uses SYSMAN commands to reset the time on all nodes in
an OpenVMS Cluster system:
$ RUN SYS$SYSTEM:SYSMAN
SYSMAN> SET ENVIRONMENT/CLUSTER
SYSMAN> SET PROFILE/PRIVILEGE=(LOG_IO,SYSLCK)
SYSMAN> CONFIGURATION SET TIME 05-JAN-2001:12:00:00
SYSMAN> EXIT
Notes
In a node that is not part of a cluster, use the SET TIME command and
specify a time. If you do not specify a time, the SET TIME command
updates the system time using the time in the TODR.
6–26 Setting System Time