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From myrna <my...@Golux.Com>
Subject Re: Faster Derby with relaxed durability
Date Tue, 15 Feb 2005 20:24:39 GMT
Mike Matrigali wrote:

>Steen Jansdal wrote:
>  
>
>>Daniel John Debrunner wrote:
>>    
>>
>>>If you build Derby yourself you can test out a faster version of Derby
>>>that has relaxed durability.
>>>By relaxed durability I mean that:
>>> - a commit no longer guarantees that the transaction's modifications
>>>will survive a system crash or JVM termination.
>>>  - the database may not recover successfully upon re-start
>>>  - a near full disk at runtime may cause unexpected errors (currently
>>>Derby ensures that space exists on the disk
>>>     for a transaction's data before commit)
>>>
>>>This is useful for unit testing or development time.
>>>I would not recommend it for production if your data is important.
>>>
>>>I think this functionality should be added into the standard Derby but
>>>in a simpler form,
>>>maybe a single property
>>>
>>>derby.storage.durable={full,none,???}  [not supported currently, see
>>>below]
>>>(or maybe even higher concept, derby.system.testMode=true??)
>>>      
>>>
[snip]

>>>Thanks,
>>>Dan.
>>>      
>>>
>>This is awesome. Please let this "not failsafe" option it be a standard
>>option. I can see a lot of places where we don't need the database to
>>be failsafe, but could use the extra speed.
>>
>>Steen
>>    
>>
>I think it is wrong to make non safe database the default, but am
>interested in hearing the communities opinion.  I do realize other
>database systems do pick this as their default.
>
>I suggest that if it is decided to
>"support" this mode that the logging system be changed to somehow
>record that the database has operated in this manner, so that if
>the database goes corrupt we don't waste effort trying to figure out
>what when wrong.  Probably need some way to mark the log records, the
>log control file and write a message to the user error log file.
>  
>
How would this work - would one be able to start the database up in 
relaxed durability mode one day, and in cautious/normal mode another 
day? Or would it be once the database is created it always stays in that 
mode?

Myrna

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