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oracle 11g

Posted on 2014-03-05
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Hi,

I would like to create a oracle sequence number as primary key in a log table.
Many applications are using this log table.
So if 2 or more applications try to update this table on "same time", then is different squence number ( seqname.nextval )   is allocated always for all the applications? or is there any chance that same sequence number allocated to 2 or more applicatinos which are trying to update same time?
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Question by:GouthamAnand
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HuaMinChen earned 600 total points
ID: 39908597
There should be only one unique sequence number being allocated to each application, as there must be still one time gap like few milliseconds when 2 application are struggling with each other at the same time.
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by:Guy Hengel [angelIII / a3]
Guy Hengel [angelIII / a3] earned 400 total points
ID: 39908615
I concur. sequence object will not return "duplicates" during operations.
to ensure, you shall have a primary key constraint on the column, and handle the case if the duplicate key error would occur.
this would happen if the sequence object is "restarted", so a new start value is given to the sequence object.
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Author Closing Comment

by:GouthamAnand
ID: 39908660
Thank you.
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Expert Comment

by:manny17
ID: 39973408
The sequence number is cached in the instance. There is no way that a same sequence number can be allocated to two different transactions. In a RAC system, the range of number cached is different on each of instance. This way oracle avoids such scenarios.
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