SYSVIEW and Daylight Savings Time (DST) change

Products

• SYSVIEW Performance Management

Issue/Introduction

Does SYSVIEW have any problems or concerns when it comes to Daylight Savings Time?

Environment

Resolution

SYSVIEW uses the TOD Clock (STCK), which is a monotonic function that is always increasing in value, to calculate intervals and elapsed times. When a DST change occurs, the STCK value does not change. Only the Time Zone Offset, which is adjusted by the Server Time Protocol (STP), is updated. To determine the local time, the TOD Clock (represented in UTC), is adjusted by the Time Zone Offset.

 

SYSVIEW saves 2 time stamps in the SMF record.

   1. One time stamp is in the header of the SMF record, that timestamp is localized with the current time zone offset.

   2. The other timestamp is a GMT STCK value that has no offset applied to it.

 

For example, the Date/Time columns on the CTRANLOG command are derived from the GMT STCK value. SYSVIEW applies the current time zone offset of your active session.  As a result, the record that is written prior to the time change, and viewed after the time change, will appear to be shifted an hour.

 

As long as the below maintenance is applied, there are no known issues with leaving SYSVIEW, SYSVUSER, and the SYSVIEW for CICS data collectors active when a DST change occurs.

If the following maintenance is not applied, the recommendation is to stop SYSVIEW, SYSVUSER, and SYSVIEW for CICS in each region prior to the DST change, and restart them afterwards. 

There is no PTF for SYSVIEW 17.0 - the code change was sourced into 17.0. 

PTF SO08743 for SYSVIEW 16.0

PTF SO08657 for SYSVIEW 15.0

 

 

 

Additional Information

When displaying log stream data (CTRANLOG, IMSTLOG, etc.) after the time zone change occurred to set the time back (Fall back), data that was recorded in the past hour (that now has a future timestamp) will not appear in the log stream until an hour passes. Adding the CUSHION 01:00:00 NODISCARD keywords to the command string (i.e., CTRANLOG CUSHION 01:00:00 NODISCARD) would allow all the records to be displayed