In this scenario, some of the target tables are subject to occasional conflicts between user updates and replicated updates. The Connect CDC solution for protecting the data integrity in this situation is to provide automatic collision resolution. This feature, which is enabled in the Replication request definition, is described in Detect collisions.
Instead of specifying a request that includes collision resolution for the targets that require it and specifying another request without collision resolution for the targets that do not require it, you specify a single request with collision resolution for all the targets. Two Replication requests for the same source table cannot be active simultaneously.
To create the Replication request:
-
From the context menu of the Requests subbranch of the distribution you just defined, select New Request>Replication.
-
On the Common tab of the Replication Request Properties dialog box, give the request a name and accept the defaults for the remaining options.
-
Do the following on the Replication tab:
-
Select a Transaction error mode setting.
The Transaction error mode setting applies to errors that occur when attempting to apply replicated data at the target. The setting is ignored if automatic collision resolution is in effect.
For this exercise, you will be specifying automatic collision resolution, so you can accept the default transaction error mode. The Transaction error mode settings are described in detail in Transaction error mode.
-
Accept the defaults Protected (shadow table) collision resolution.
Shadow table collision resolution is designed for bi-directional replication, and the replication in this scenario is unidirectional. For more information about bi-directional replication, see Bi-directional replication.
-
Specify Unprotected collision resolution settings.
-
Select the type(s) of user updates (INSERT, UPDATE, and/or DELETE) you want Connect CDC to resolve automatically.
For this exercise, we resolve all three types of collisions.
Note: If you select None (error) for any of the Unprotected collision resolution options, any collisions of that type will be subject to transaction error mode handling.-
Select whether you want the replicated data change or the target data condition to be assumed correct.
For this exercise, we assume the replicated source data to be correct:
If a source INSERT encounters an existing record, for example, the target record is updated to match the source. If the Target correct, ignore option is selected for this replicated INSERT, the source operation is discarded, and the target row is left as is.
-
-
Select Enable Transaction Bundling.
-
Transaction bundling enables you to bundle smaller transactions captured on the source database and apply them as a single larger transaction on the target database. This approach has been shown to significantly increase performance depending on the target database. When you use this option, the kernel, on the target side, gathers contiguous groups of small source transactions and applies them as larger transactions at the target. Enable Transaction Bundling is unchecked by default.
Transaction bundling cannot be used for a request:
-
That has at least one target that is an Informix database
-
For bi-directional mapping
-
When the target database is a file system
Also, specify the Transaction Bundling Limit (50-500). Specify the desired number of rows to be bundled. The valid range is from 50 to 500. The default value is 300.