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Topic Title: Threaded CM Synergy Sessions
Topic Summary: Placing a CM Synergy session inside a thread often causes baseline to fail
Created On: 26-Jan-2006 09:30
Status: Read Only
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Answer This question was answered by David Hope, on Tuesday, January 31, 2006 2:00 PM

Answer:
Fantastic this is exactly what i wanted to know!! Thanks Toni
 26-Jan-2006 09:30
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David Hope

Posts: 5
Joined: 22-Jul-2005

Hi All,

I have written a multithreaded build process which also creates a baseline at the end, the trouble is that when you launch 6 threaded baseline processes synergy often fails, either randomly or by saying that the database is busy.

I take it CM Synergy is not thread safe and i must baseline sequentially rather than in parallel?

Thanks and Regards,

David Hope
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 30-Jan-2006 11:20
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Toni Arte

Posts: 30
Joined: 16-Aug-2004

This really boils down to the Informix locking model, i.e. in Informix a reader will place a lock on a row it wishes to read in order to prevent writes. Multiple sessions can run into problems with this, i.e. two sessions both need a lock the other one has in order to continue. The database detects this and fails the other operation, the Synergy/CM reports thsi as 'Database is busy' error to the end-user. But what really happens in the background is a deadlock.

Based on my experience, these are not too frequent in real life, but using a lot of parallel operations in scripts can easily trigger this problem (you just need to checkout the 'tutorial' project from the tutorial database for 'Insulated Development' purpose in parallel, using different 'release' for each checkout).

This problem relates to the creation of new project objects, and it is supposed to be much better in Synergy/CM 6.4. I have also not been able to reproduce it on Synergy/CM 6.3 Oracle release (in Oracle, a reader never locks anything, the read consistency is handled in a different way).
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 31-Jan-2006 14:00
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David Hope

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Joined: 22-Jul-2005

 



Edited: 31-Jan-2006 at 14:01 by David Hope
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 31-Jan-2006 14:00
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David Hope

Posts: 5
Joined: 22-Jul-2005

Answer Answer
Fantastic this is exactly what i wanted to know!! Thanks Toni
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