File-based download is an alternative way to download data to SQL Anywhere remote databases: downloads can be distributed as files, enabling offline distribution of synchronization changes. This allows you to create a file once and distribute it to many remote databases.
With file-based download, you can put download synchronization changes in a file and transfer it to SQL Anywhere remote databases in any way a file can be transferred. For example, you can:
broadcast the data by satellite multicast
apply the update using Sybase Afaria
email or FTP the file to users
You choose the users you want to receive the file. Full synchronization integrity is preserved in file-based download, including conflict detection and resolution. You can ensure that the file is secure by applying third-party encryption on the file.
File-based downloads are useful when a large amount of data changes on the consolidated database, but the remote database does not update the data frequently or does not do any updates at all. For example, price lists, product lists, and code tables.
File-based downloads are not useful when the downloaded data is updated frequently on the remote database or when you are running frequent upload-only synchronizations. In these situations, the remote sites may be unable to apply download files because of integrity checks that are performed when download files are applied.
File-based downloads currently can be used only with SQL Anywhere remote databases.
In most cases, you should use a download-only publication for your file-based download. Use a regular publication only when you need to perform uploads with the same publication as you perform file-based downloads.
See Download-only publications.
If you use a regular publication, file-based downloads cannot be used as the sole means of updating remote databases. In that case you still need to regularly perform full synchronizations or upload-only synchronizations. Full or upload-only synchronizations are required to advance log offsets and to maintain the log file, which otherwise will grow large and slow down synchronization. A full synchronization may also be required to recover from errors.