"Methodology" <Methodology@discussions.microsoft.com> wrote in message
news:11FFC510-9BBE-46C8-A0E6-A201D724D7F1@microsoft.com...
> and subsequent uncommitted transactions can be referenced in queries
> through
> 'nolock'?
>
> "Hilary Cotter" wrote:
>
>> Answers inline.
>> "Methodology" <Methodology@discussions.microsoft.com> wrote in message
>> news:9B81CC06-14D6-4B53-86C0-0A881C6CC25C@microsoft.com...
>> > this link
>> >
>> > http://msdn2.microsoft.com/en-us/library/ms179344.aspx
>> >
>> > say this:
>> >
>> > " The principal server writes the transaction to the database and,
>> > concurrently, sends the log record to the mirror server. The principal
>> > server
>> > waits for an acknowledgement from the mirror server before confirming
>> > either
>> > of the following to the client: a transaction commit or a rollback. "
>> >
>> This is for the high safety mode.
>> > however this link:
>> >
>> > http://www.microsoft.com/technet/prodtechnol/sql/2005/dbmirror.mspx
>> >
>> > say this:
>> >
>> > "Most importantly, unlike a distributed transaction, failures to commit
>> > on
>> > the mirror will not cause a transaction rollback on the principal."
>> >
>>
>> read the complete section - specifically this.
>>
>> "When the principal receives its response from the mirror, the principal
>> can
>> then proceed to the next hardening.
>> Despite the close coordination between principal and mirror when safety
>> is
>> FULL, database mirroring is not a distributed transaction and does not
>> use a
>> two-phase commit.
>>
>> . In database mirroring, you have two transactions being played out
>> on
>> two servers, not one transaction distributed across them.
>>
>> . Database mirroring does not use the partner servers as resource
>> managers in a distributed transaction
>>
>> . Database mirroring transactions do not go through prepare and
>> commit
>> phases.
>>
>> . Most importantly, unlike a distributed transaction, failures to
>> commit on the mirror will not cause a transaction rollback on the
>> principal.
>>
>>
>> "
>>
>> Tha transaction is hardened on the principal and then written to the
>> mirror.
>> Where it is hardened there. Then the next transaction can be hardened on
>> the
>> log buffer on the principal. What will happen is that at some point
>> later
>> subsequent transactions will fail to be committed on the principal.
>>
>> > so which is it? failure of ack reponse from mirror DOES or DOES not
>> > cause
>> > a
>> > rollback at some level on the primary?
>> >
>>
>>
>>