[Info-vax] Databases versus RMS

[Arne Vajhøj]

On 4/18/2012 10:11 AM, Richard B. Gilbert wrote:
> On 4/17/2012 2:52 PM, JF Mezei wrote:
>> A web forum has been down for over 24 hours now because of a power
>> failure. Seems their database "broke".
>>
>> Since there are few teenagers here, I figured I might get some "senior"
>> opinions.
>>
>> Are database engines so fragile that a power failure will truly wreak
>> havok on a database requiring time consuming work and debugging ?
>
> Some are. Some are not. The expensive ones, e.g. Oracle, should survive
> without problems.
>
> My failing memory recalls something that was called "two phase commit"
> or something like that. You write what you're going to do and then you
> do it. On a successful commit, you mark the transaction complete. If
> your commit fails, you have all the pieces necessary to recover.

2PC is only necessary if you have more than one data source (database
or other).

You can have a log and recover from that without 2PC.

Arne