Capture Process

The Capture process follows rules that define, dictate, or decide if the Capture process has to extract or discard the database changes into LCR events. The rules can be specified in a positive or negative rule set for the Capture process. If a rule evaluates to TRUE for a change and the rule is in the positive rule set for a Capture process, the change is captured.

If a rule evaluates to TRUE for a change and the rule is in the negative rule set for a Capture process, the change is discarded. If a Capture process has both a positive and a negative rule set, the negative rule set is always evaluated first.

Salient Features

In a typical Streams configuration, for administrative and performance reasons, multiple Capture processes can be created. When the DBA wants to have different sets of data streams going to different destinations with data that may vary in nature, multiple Capture processes should be considered.

The Capture process has to be associated with pre-created queues. It is possible to use one queue associated with the multiple capture processes. Oracle recommends that each Capture process use a separate queue to help keep the LCRs from different capture processes separate.

The streams_pool_size initialization parameter controls the size of the Streams Pool within the SGA of the database. This parameter was newly introduced in Oracle10g database. In earlier versions, there was no way that the allocated SGA resources for streams could be increased except by increasing the total SGA size. Oracle10g provides a way to have better control over the memory resources allocated for Streams.