The snapshot for this publication has become obsolete.

We are using sql server 2005 and in our TEST environment --please note
TEST-- I have set the subscription expiration interval to be 1 day.
We made the mistake in the beginning of setting it to never expire and
we are getting errors, performance problems etc.  I am trying to test
the behavior of changing that setting.

What I did was, after I set it to 1 day, I re-ran the snapshot.  Fine,
it all worked for devices currently synching.  24 hours later, I tried
to create a new subscription and I get "The snapshot for this
publication has become obsolete. The snapshot agent needs to be run
again before the subscription can be synchronized."  So fine, I reran
the snapshot, THEN 24 hours later I try to create a new subscription
and I get "The snapshot for this publication has become obsolete. The
snapshot agent needs to be run again before the subscription can be
synchronized." ...notice a trend.

I understand the concept of snapshots, subscriptions, and
publications.  I know where they fit into the puzzle, but this
behavior is strange.

I am thoroughly confused, I am setting a publication setting called
supposed to do..if a subscription doesn't connect within stated time
frame, it's expired...wonderful that is what I am after.

Why is it that the Snapshot is becoming obsolete on a new
subscription?  My understanding of a snapshot is that it would not
become obsolete unless there are schema changes, filter changes,
etc..then you would have to re-init, but this is on a new
subscription.

By this logic, if I set the subscription expiration to 14 days, I
would have to generate a new snapshot every 13 days?  This just
doesn't seem right...

Sorry so long, any ideas?

For PDAs you should set it to something smallish, but 1 day is too small.

For PDAs you should set it to something smallish, but 1 day is too small. I
think 4-5 days is a good number.

The snapshot contains all the data, schema and metadata required to create
all the objects on the subscriber. After one day in your case the metadata
on the publisher is purged and what is in the snapshot will not be
sufficient to sync with the publisher, hence you need a new snapshot.

You want to set a small number so that not a lot of data goes across the
wire, but a big enough number so that the majority of your subscribers will
sync within the expiration time. If you set it to an infinite amount - never
expires, a lot of data will have to go to the subscriber to get it back in
sync.

I find that sometimes its better to send a new snapshot to your pda's
regularly as sometimes the sync times can be more lengthy than deploying an
initial snapshot.

--
Hilary Cotter

Looking for a SQL Server replication book?
http://www.nwsu.com/0974973602.html

Looking for a FAQ on Indexing Services/SQL FTS
http://www.indexserverfaq.com

The answer lies in the MSmerge_contents and MSmerge_genhistory tables.

The answer lies in the MSmerge_contents and MSmerge_genhistory tables.
These two tables hold the list of data changes that happened for the
past x days, x being the subscription expiration days. After x days the
record of the data change expire from the MSmerge_contents table. The
implication of that is that existing subscriptions that have not
synchronised for the past x days will then not be able to merge that
change anymore. The same holds true for creating new subscriptions with
an old snapshot - remember the snapshot also contains data. If the
snapshot was created x-2 days ago you will missing two days of data
changes that has already expired from the MSmerge_contents table.

Thanks JE, I have some followup thoughts/questions to your post.

Thanks JE, I have some followup thoughts/questions to your post.

an old snapshot "

I still do not understand what makes it an old snapshot.  I understand
that if a subscription expires, I will not be able to see data in a
new subscription from the expired subscription, but I should be able
to create a new subscription with the information that the snapshot
has.  I do not understand how the snapshot is valid with an existing
subscription A but obsolete with a new subscription B.

The snapshot for this publication has become obsolete.

The snapshot is only really used once: to initialise the subscriber. It
contains the schema and data for the initial load before replication
starts. Subscriber expiry indicates the amount of days that a log of
data changes are kept. For example let us take a snapshot that is 10
days old and the subscriber expiry is set to 5 days. The snapshot will
be consistent with the publisher 10 days ago, but your log of changes at
the publisher only goes back 5 days. Which means a new subscriber will
never be able to catch up - it will always be missing those 5 days of
data. Existing subscribers will not be affected by an old snapshot -
they don't need it again after initialisation.

The snapshot for this publication has become obsolete. DG

So if I understand correctly,  creating the new snapshot will not affect the existing subscriptions that have been kept up to date?



If I have a remote user that is inconsistently updating the subscription, will have to keep a "fresh" snapshot to keep that subscriber maintained?