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SQL Anywhere 11.0.0 » MobiLink - Client Administration » Introduction to SQL Anywhere Clients for MobiLink » MobiLink SQL Anywhere client utility [dbmlsync]


-tu option

Specifies that each transaction on the remote database should be uploaded as a separate transaction within one synchronization.

dbmlsync -tu ...

When you use -tu, you create a transactional upload: dbmlsync uploads each transaction on the remote database as a distinct transaction. The MobiLink server applies and commits each transaction separately when it is received.

When you use -tu, the order of transactions on the remote database is always preserved on the consolidated database. However, the order of operations in a transaction may not be preserved, for two reasons:

  • MobiLink always applies updates based on foreign key relationships. For example, when data is changed in child and parent tables, MobiLink inserts data into the parent table before the child table, but deletes data from the child before the parent. If your remote operations do not follow this order, the order of operations differ on the consolidated database.
  • Operations within a transaction are coalesced. This means that if you change the same row three times in one transaction, only the final form of the row is uploaded.

If a transactional upload is interrupted, the data that was not sent is sent in the next synchronization. In most cases, only the transactions that were not successfully completed are sent at that time. In some cases, such as when the upload failure occurs during the first synchronization of a subscription, dbmlsync resends all transactions.

When you do not use -tu, MobiLink coalesces all changes on the remote database into one transaction in the upload. This means that if you change the same row three times between synchronizations, regardless of the number of remote transactions, only the final form of the row is uploaded. This default behavior is efficient and is optimal in many situations.

However, in certain situations you may want to preserve remote transactions on the consolidated database. For example, you may want to define triggers on the consolidated database that act on transactions as they occur in the remote database.

In addition, there are advantages to breaking up the upload into smaller transactions. Many consolidated databases are optimized for small transactions, so sending a very large transaction is not efficient or may cause too much contention. Also, when you use -tu you may not lose the entire upload if there are communications errors during the upload. When you use -tu and there is an upload error, all successfully uploaded transactions are applied.

The -tu option makes MobiLink behave in a manner that is very close to SQL Remote. The main difference is that SQL Remote replicates all changes to the remote database in the order they occur, without coalescing. To mimic this behavior, you must commit after each database operation on the remote database.

You cannot use -tu with the Increment extended option or with scripted uploads.

See also