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From: robert engels <rengels@ix.netcom.com>
Subject: Re: [jira] Resolved: (LUCENE-1044) Behavior on hard power shutdown
Date: Sat, 3 Nov 2007 19:16:39 -0500
To: java-dev@lucene.apache.org

See my previous email.

I have written several 'atomic' ACID systems in java. It is VERY EASY  
TO DO. Read any introductory (academic) book on database systems.

On Nov 3, 2007, at 7:08 PM, Mark Miller wrote:

> Derby does not guarantee atomicity? Other java DB's? I thought they  
> did, but perhaps not. You cannot rig a simple system with some sort  
> of rename call?
>
> If a hard power shutdown interrupted, on the next start the system  
> could ideally be left in a condition that uses the previous commit  
> point, or recognize the latest commit failed, clean it up, and go  
> back to the previous commit point. There must be ways to do it that  
> don't rely on a buffer being fully flushed, but rather on atomic  
> file system operations (of which there must be some that can be  
> counted on in java?).
>
> Chris Hostetter wrote:
>> : Is the new autocommit=false code atomic (the new check point is  
>> successfully
>> : made and moved to or its not)? If not I imagine it could be made  
>> to be without
>> : too much work right?
>>
>> No matter what work we do in Java code to try and garuntee  
>> atomicity, the JVM can't garuntee that File IO buffers are flushed  
>> unless the JVM is shutdown cleanly, so i don't see how we could  
>> possibly make any claims
>> of atomicity in the event of hard process (or OS) termination.
>>
>> i'd be happy to be proven wrong by someone who knows more about  
>> IO, filesystems, and the JVM Specification.
>>
>>
>>
>> -Hoss
>>
>>
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