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SQL Anywhere 10.0.1 » MobiLink - Server Administration » Synchronization Techniques » Handling failed downloads

Handling failed downloads Next Page

Resuming failed downloads

Download failure is caused by a communication error during download or a user aborting the download. MobiLink has functionality that helps you recover from download failure, and may help you avoid having to retransmit the entire download. This functionality has separate implementations for SQL Anywhere and UltraLite remote databases.

SQL Anywhere remote databases

When synchronization fails during a download, none of the download is applied to the remote database. However, the part of the download that was successfully transmitted is stored in a temporary file on the remote device. You cannot access this file directly, but dbmlsync provides functionality that makes use of the file. When you use this functionality, you may be able to avoid lengthy retransmission of data. You may also be able to recover from download failure automatically.


The download cannot be resumed when the SendDownloadACK extended option is set to ON (the default is OFF) or when the DownloadBufferSize extended option is set to 0 (which is also not the default).

There are three ways to implement this functionality. In all cases, the resumed download will fail if there is any new data to be uploaded, and dbmlsync will abort.

UltraLite remote databases

You can control the behavior of UltraLite applications following a failed download as follows:

For more information about communications errors, see SQL Anywhere® 10 - Error Messages.


If the send_download_ack synchronization parameter is set to true (which is not the default), the setting will be ignored for the resumed download.