SQL Anywhere Mobile - Timestamp question

Author

Timestamp question

Nim Vadgama

2005-10-31, 11:24 am

Hi

I'm using version 9.0.2.3198 + ASA remote + ASE
consolidated) and have 2 questions.

Firstly, you advise users to create triggers on the
consolidated tables to update the last update date. We
already have an application which updates this field when a
corresponding record.

For the remote db, when the record is uploaded can I not
send a GETDATE() to the consolidated database in the
upload_insert and upload_update. Would this cause any sync
issues?
If I upload the remote db record timestamp this may be too
old for another remote user, who may have synchronized since
then.

Secondly, is the ml_subscription last_upload_time and
last_download_time used or should we only use the times on
the syssync table. If so why why does the last_download_time
get updated with the last_upload_time on the next sync in
ml_subscription?

Many Thanks
Nimesh

Greg Fenton

2005-10-31, 1:23 pm

Nim Vadgama wrote:
> We
> already have an application which updates this field when a
> corresponding record.

Note that the column maintained in the consolidated to track the last
modification date for a row (often refered to as the "last_modified"
column), is for synchronization purposes only and should not be used in
any way by an application. If you need a date field for the
application, make it a separate one from the synchronization.

> For the remote db, when the record is uploaded can I not
> send a GETDATE() to the consolidated database in the
> upload_insert and upload_update. Would this cause any sync
> issues?

If the last_modified is only used for synchronization purposes, then why
can you not update this field during the upload?

> If I upload the remote db record timestamp this may be too
> old for another remote user, who may have synchronized since
> then.

You definitely do not want to use a timestamp from the remote. The
last_modified column should not be synchronized as it only has real
meaning on the consolidated (i.e. don't put it in your publication).
Also, if you do try to rely on remote date fields, you need to ensure
the remote and consolidated clocks are in synch (which is outside of
MobiLink functionality).

> Secondly, is the ml_subscription last_upload_time and
> last_download_time used or should we only use the times on
> the syssync table. If so why why does the last_download_time
> get updated with the last_upload_time on the next sync in
> ml_subscription?

I'm not sure what you are refering to. The ml_subscription table holds
values at the *consolidated* that are maintained by MobiLink. The
syssync table holds values for the *remote* that are maintained by dbmlsync.

What is it you are looking to do with these values?

greg.fenton
--
Greg Fenton
Consultant, Solution Services, iAnywhere Solutions
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