1954578 - Changing the operating system clock while ASE is running - SAP ASE | SAP Knowledge Base Article

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1954578 - Changing the operating system clock while ASE is running - SAP ASE

Symptom

Adaptive Server Enterprise (ASE) has an internal clock that is initialized at start time with the current value of the operating system clock
and incremented based on regular SIGALRM signals from the operating system (typically 10 per second).  The internal clock is
used to avoid the overhead of frequent system function calls to get the current time.
Once a minute, ASE polls the operating system clock to get the actual current time value.
 
The two clocks sometimes fall slightly out of synchronization.
When this happens, ASE speeds up or slows down the internal clock to reduce the difference with the operating system clock. 
When the operating system clock is set ahead,  pending alarms are delivered as their time is overdue,
but if the operating system clock is turned back SIGALRM delivery may be delayed causing waitfor or dump commands to hang.


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Environment

SAP Adaptive Server Enterprise (ASE) all versions

Product

SAP Adaptive Server Enterprise 12.5 ; SAP Adaptive Server Enterprise 15.7 ; SAP Adaptive Server Enterprise 16.0

Keywords

ASE, internal, clock, operating system, OS, hang, hung, sync , KBA , BC-SYB-ASE , Sybase ASE Database Platform (non Business Suite) , Problem

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