Re: Mirroring by RRN slow for large file -- MIDRANGE-L

Peter,

I haven't actually tested the performance of RRN vs. keyed index access on
IBM i, but the IBM i index search may actually return a RRN if it works
like some of the other DBMS products I've worked with. So a known RRN may
be the quickest way to find records.

I'm not that familiar with iTera, but I wonder if it may have a
configuration setting that controls the queue on the target system?

Nathan.

On Sat, Aug 12, 2017 at 11:39 PM, Peter Connell <Peter.Connell@xxxxxxxxxxx>
wrote:

I assume that mirroring software (ITERA) that uses journals for
replication to another IBM i5 performs updates and deletes on the target
system by using the RRN stored in each journal to replicate the update or
delete.
This is a reasonable assumption since the mirroring software knows nothing
about any index it might use to achieve the update of delete via an access
path.

A large file on the source system of 170 million records which may attract
several million updates and deletes in a day results in these being queued
for long periods on the target system before the actual replication event
occurs to keep the file in synch.
I presume that the substantial latency observed between the source and
target updates and deletes is because the record be updated or deleted is
being located via RRN.
Perhaps this is because DB2 has to do a table scan to find the record
which is slower than an update via a unique index.

It's not clear if creating an index whose primary key is RRN would help
otherwise the only solution may be to do a custom replication that reads
the journal, and extracts the unique index to do an update or delete.

Regards, Peter

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