Re: Failed transactions

Klaus,

I am discussing the likelihood that I will someday be faced with out  
of memory problems and yes, once you've popped your memory, you have  
no idea what your app will do for any given user action, no doubt  
about it.  That is precisely why I am bringing it up, the scenario is  
very real.  My customers will quickly eat up all the memory / data  
space I give them and then demand more.  My responsibility is to do  
the maximum possible to protect my customers data.  At the same time,  
I would like to give them as much speed as possible, hence my being  
here.

If a computer goes down during a db transaction you lose the  
transaction and it is not re-attemped when you come back.  That is a  
perfectly reasonable expectation.   With Prevayler, the failed  
transaction will reattempt unless I tell the system otherwise.

If the last transaction fails due to a lack of available memory,  it  
is reasonable to assume that the same thing could happen if I come  
back up and re-run the transaction.  I am going to have to manage that  
somehow and I ask again, how (if at all) has anyone out there prepared  
for this scenario?   All systems have strengths and weaknesses, and I  
don't mind dealing with prevayler's weaknesses to get it's benefits,  
but I do need to understand them in gory detail.

Thanks,

R

On Jul 31, 2009, at 2:50 PM, Klaus Wuestefeld wrote:

> There is a more general question that you have to answer anyway,
> regardless of how you do your persistence, Prevayler or otherwise:
>
> "My system is in a state that will crash given some common basic user
> action. What now?"
>
> See you, Klaus.
>
>
>
> On Fri, Jul 31, 2009 at 5:28 PM, Ross Rick<[email protected]> wrote:
>> If read the previous thread correctly...   a transaction is  
>> journaled to the
>> disk prior to execution on the model.
>> If the transaction fails, does the journaled transaction always get  
>> removed
>> from disk?   It would appear that the transaction is removed from  
>> disk under
>> normal circumstances, but under catastrophic failure, it's less  
>> clear.
>> In fact, I doubt that it is entirely possible to ensure any such  
>> thing.
>> How do the rest of you handle this?   When you come back up your  
>> system will
>> attempt the transaction again, even if it works, that is not the  
>> expected
>> state of the system.   The expected state is the state just prior to
>> attempting the bad transaction.
>> How am I doing on the understanding here?   I appreciate everyone's  
>> help
>> very much.
>>
>> R
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>
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