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SQL Anywhere 11.0.0 » MobiLink - Client Administration » Introduction to SQL Anywhere Clients for MobiLink » SQL Anywhere clients » Publishing data

 

Download-only publications

You can create a publication that only downloads data to remote databases, and never uploads data. Download-only publications do not use a transaction log on the client.

Differences between download-only methods

There are two ways to specify that only a download (and not an upload) should occur:

  • Download-only synchronization¬†¬† Use the dbmlsync options -e DownloadOnly or -ds.

  • Download-only publication¬†¬† Create the publication with the FOR DOWNLOAD ONLY keyword.

The two approaches are quite different:

Download-only synchronizations Download-only publications
If the download attempts to change rows that have been modified on the remote database and not yet uploaded, the download fails. The download can overwrite rows that have been modified on the remote database and not yet uploaded.
Uses a normal publication that can be uploaded and/or downloaded. Download-only synchronization is specified using dbmlsync command line options or extended options. Uses a download-only publication. All synchronizations on these publications are download-only. You cannot alter a normal publication to make it download-only.
Requires a log file. Does not require a log file.
The log file is not truncated when these subscriptions are not uploaded for a long time, and can consume significant amounts of storage. If there is a log file, the synchronization does not affect the synchronization truncation point. This means that the log file can still be truncated even if the publication is not synchronized for a long time. Download-only publications do not affect log file truncation.
You need to do an upload occasionally to reduce the amount of log that is scanned by the download-only synchronization. Otherwise, the download-only synchronization takes an increasingly long time to complete. There is no need to ever do an upload.
See also