Re: HA Setup Review

Thank you for your response Ron and apologies for delayed response.

"The *guarantee* that all transactions committed on the primary have been
written to the secondary just before shutting down Primary." -> Is this for
SYNC or ASYNC?

Thanks for clarifying that the transactions would be blocked if the
network/WAN link is down.

"Thus... you leave replication to the remote DR site in asynchronous mode
until that very specific point when you need to guarantee remote
consistency: *just before* you shut down the Primary for patching.

Once the Primary is patched, and replication is restored, then you can
change back to async mode." -- Makes sense now. Thanks a lot for
clarifying.

On Fri, May 3, 2024 at 8:55 AM Ron Johnson <ronljohnsonjr(at)gmail(dot)com> wrote:

> On Tue, Apr 30, 2024 at 12:30 PM akshay polji <akshay(dot)polji(at)gmail(dot)com>
> wrote:
>
>> ---- Point - 3
>> "You can switch from async to sync replication just before patching, and
>> then switch back to async when it's completed." --> I am a little confused
>> here. What benefit do we get by switching from async to sync replication
>> before patching?
>>
>
> The *guarantee* that all transactions committed on the primary have been
> written to the secondary just before shutting down Primary.
>
>
>> I mean that would block the transactions on the primary DB right?
>>
>
> Wrong 99.99% of the time. It *blocks* the transaction *IFF the
> network/WAN link is down*.
>
> When the WAN link is up, you "just" get cascading transaction *slowness* because
> of WAN latency.
>
> Thus... you leave replication to the remote DR site in asynchronous mode
> until that very specific point when you need to guarantee remote
> consistency: *just before* you shut down the Primary for patching.
>
> Once the Primary is patched, and replication is restored, then you can
> change back to async mode.
>