ADSM-L

TSM and Time zone/daylight savings time FAQ Technote#1164535

2004-03-30 10:45:16
Subject: TSM and Time zone/daylight savings time FAQ Technote#1164535
From: Sam Giallanza <giallanz AT US.IBM DOT COM>
To: ADSM-L AT VM.MARIST DOT EDU
Date: Tue, 30 Mar 2004 08:44:36 -0700




New technote on Daylight Savings Time (TSM).

                                                                       
                                                                       
 Title *             TSM and Time Zone/Daylight Savings Time FAQ       
 
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                     This document describes how Tivoli Storage Manager (TSM) 
is affected
                     by time zone differences and Daylight Savings Time 
adjustments.
                                                                       
 
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                     TSM Scheduled Events                              
                     When using TSM's scheduling facilities, all scheduling 
dates and
                     times are based on the TSM server host machine's system 
clock. This
                     is generally not an issue when all TSM client machines are 
in the
                     same time zone as the TSM server machine. In cases where 
the TSM
                     server host machine's clock may differ from a client 
machine - for
                     example, the server machine is located in New York and the 
client
                     machine is located in California - then the difference 
must be taken
                     into account when scheduling activity for that client. New 
York is
                     three hours ahead of California, so if the client activity 
needs to
                     begin at 8:00 PM local time (local to the client), then 
the schedule
                     on the server must be defined to begin at 11:00 PM local 
time (local
                     to the server).                                   
                                                                       
                     NOTE: For the purposes of discussion, it is assumed that 
system
                     clocks are set to their respective local time zones unless
                     explicitly stated otherwise.                      
                                                                       
                     The Effect of Daylight Savings Time               
                     Suppose that the same TSM server described above has a TSM 
client
                     located in Arizona. The state of Arizona does not observe 
Daylight
                     Savings Time (DST). While New York observes Standard Time, 
it is two
                     hours ahead of Arizona. While New York observes DST, it is 
three
                     hours ahead of Arizona. Thus if the client activity must 
begin at
                     8:00 PM local time, the schedule on the server must be 
defined to
                     begin at 10:00 PM during Standard Time and changed to 
11:00 PM
                     during DST.                                       
                                                                       
                     What happens when the client machine's system time is 
changed
                     This situation presents no difficulty. The TSM client 
starts logging
                     new messages with the current (new) system time.  
                                                                       
                     What happens when the server machine's system time is 
changed
                     The TSM server performs a date and time ("date") check 
whenever it
                     is started, and each hour thereafter. If the server 
detects an
                     invalid date, then client sessions are disabled and 
expiration,
                     migration, reclamation, and volume history deletion 
operations are
                     disallowed. You either need to fix the system date if it 
is indeed
                     in error, or else use the TSM administrative command 
ACCEPT DATE to
                     force the server to accept the current date as valid. In 
this case
                     you must follow the ACCEPT DATE command with ENABLE 
SESSIONS in
                     order to re-enable the server for client sessions.
                                                                       
                     The TSM server treats any of the following as an invalid 
date:
                                                                       
                     - Earlier than the date the TSM server was installed.
                                                                       
                     - More than one hour earlier than the last time the date 
was
                     checked.                                          
                                                                       
                     - More than 30 days later than the last time the date was 
checked.
                                                                       
                     One-hour changes forward or back for DST are considered 
valid.
                                                                       
                     Generally there are no problems when the TSM server 
machine's date
                     is changed. The most typical changes occur when changing 
between DST
                     and Standard Time. Considerations for these changes 
include:
                                                                       
                     - Scheduled activity between TSM client and server that 
reside in
                     different time zones, as discussed above.         
                                                                       
                     - Scheduled activity that may not run. If a scheduled 
event is to
                     occur between the current system time and the new system 
time, then
                     the event may be missed for that day. For example, suppose 
client
                     activity is scheduled to run between 2:15 AM and 2:45 AM 
(the
                     schedule start time is 2:15 AM and the window is 30 
minutes). If the
                     current time is 2:00 AM and the system time is advanced 
one hour to
                     change to DST, then the new system time will be 3:00 AM. 
The server
                     will thus treat the scheduled event as "Missed". The 
exception is
                     for clients that use SCHEDMODE POLLING: their scheduled 
activity
                     will still run. But the server will not prompt clients 
that run with
                     SCHEDMODE PROMPTED. This situation can be avoided by 
changing the
                     system time such that no scheduled activity falls between 
the
                     current time and the new time.                    
                                                                       
                     When the system time is regressed then all scheduled 
activity should
                     still run to completion. Scheduled events that occur 
between the
                     current system time and the new time will not execute 
twice. For
                     example, suppose client activity is scheduled to run 
between 2:15 AM
                     and 2:45 AM (the schedule start time is 2:15 AM and the 
window is 30
                     minutes). If the activity has already occurred and the 
current time
                     is 3:00 AM, then if the system time is regressed one hour 
to
                     Standard Time (so the new time is 2:00 AM), the 2:15 AM 
event will
                     not run again when the clock reaches 2:15 AM.     
                                                                       
                     Known problems and limitations                    
                     When the system time is changed on z/OS systems, the TSM 
server
                     address space must be shut down and restarted in order to 
pick up
                     the new system time. On all other platforms, when the 
system time is
                     changed the TSM server automatically begins to use the new 
system
                     time.                                             
                                                                       
                     The following defect exists in TSM server versions below 
5.2.2.0. It
                     is fixed in TSM server version 5.2.2 and higher.  
                                                                       
                     PQ73834 - TSM server problem - Message "ANR9999D 
SMNODE(nnn):
                     ThreadId<mmm> Error 19 initializing object set" occurred 
when trying
                     to restore from a backup set that was created on or around 
the
                     change between Standard Time and DST in a prior year. See
                     http://www-1.ibm.com/support/docview.wss?uid=swg1PQ73834 
for further
                     information.                                      
                                                                       
                     The following defects existed in client versions that are 
no longer
                     supported.                                        
                                                                       
                     IC13012 - TSM client for Windows problem - When a change 
between DST
                     and Standard Time occurred on the client machine, the first
                     incremental backup of FAT partitions after the time change 
resulted
                     in all files being backed up, even if the files hadn't 
changed. This
                     problem existed in early ADSM version 2.1 Windows clients. 
It is
                     corrected in version 2.1, level 0.5 and later. Due to the 
age of
                     this defect and the affected clients, further information 
is not
                     available on the web.                             
                                                                       
                     IC28544 - TSM client for Windows problem - When changes 
between DST
                     and Standard Time occurred on the client machine 
automatically via
                     the Windows feature "Automatically adjust clock for 
Daylight Savings
                     Changes", the first incremental backups of NTFS partitions 
after the
                     time change resulted in all files being backed up, even if 
the files
                     didn't change. (The problem did not occur if the time was 
adjusted
                     manually.) This problem existed in TSM client versions 
3.7.2, 4.1.0,
                     and 4.1.1. It has been corrected in subsequent versions. 
See
                     http://www-1.ibm.com/support/docview.wss?uid=swg1IC28544 
for further
                     information.                                      
                                                                       
                                                                       
 
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 Topic               Daylight savings time , DST TSM server client     
 
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Cordially,

Sam J. Giallanza
Tivoli Certified Consultant
Field Issues Manager
Field Input Communications (FIC)
giallanz AT us.ibm DOT com
520.799.5512 - T/L 321.5512

Our new web Support site and KB is at :

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