GoldenGate Architecture

Overview of GoldenGate Components Continued

5) Extract Files :-

- When you want to do processing a one-time run,such as an initial load or a batch run that synchronizes transactional changes,GoldenGate stores the extracted changes in an extract file instead of a trail.
- The extract file mostly is a single file but can be configured to split into multiple files in anticipation of limitations on the size of a file that are imposed by the operating system. In this sense,it is similar to a trail,except that checkpoints are not recorded.
- The file or files are created automatically during the run.Versioning features that apply to trails also apply to extract files.

6) Checkpoints :-

- Checkpoints store the current read and write positions of a process to disk for recovery purposes.Checkpoints ensure that database changes marked for synchronization are extracted by Extract and replicated by Replicat to prevent redundant processing.
- They provide fault tolerance by preventing the loss of data when the system,the network,or a GoldenGate process need to be restarted.For advanced synchronization configurations, checkpoints enable multiple Extract or Replicat processes to read from the same set of trails.
- The read checkpoint of a process is always synchronized with the write checkpoint.Thus,if GoldenGate needs to re-read something that it already sent to the target system (for example,after a process failure) checkpoints enable accurate recovery to the point where a new transaction starts, and GoldenGate can resume processing.
- Checkpoints work with inter-process acknowledgments to prevent messages from being lost in the network.Extract creates checkpoints for its positions in the data source and in the trail. Replicat creates checkpoints for its position in the trail.
- A checkpoint system is used for Extract and Replicat processes that operate continuously,but it is not required for Extract and Replicat processes that run in batch mode. A batch process can be re-run from its start point, whereas continuous processing requires the support for planned or unplanned interruptions that is provided by checkpoints.
- Checkpoint information is maintained in checkpoint files within the dirchk sub-directory of the GoldenGate directory. Optionally,Replicat’s checkpoints can be maintained in a checkpoint table within the target database,in addition to a standard checkpoint file.

7) Manager :-

- Manager is the control process of GoldenGate. Manager must be running on each system in the GoldenGate configuration before Extract or Replicat can be started, and Manager must remain running while those processes are running so that resource management functions are performed.

Manager performs the following functions:
- Monitor and restart GoldenGate processes.
- Issue threshold reports, for example when throughput slows down or when synchronization latency increases.
- Maintain trail files and logs.
- Allocate data storage space.
- Report errors and events.
- Receive and route user requests from the user interface.

One Manager process can control many Extract or Replicat processes. On Windows systems, Manager can run as a service.

8) Collector :-

- Collector is a process that runs in the background on the target system. Collector receives extracted database changes that are sent across the TCP/IP network, and it writes them to a trail or extract file.
- Manager starts Collector automatically when a network connection is required. When Manager starts Collector, the process is known as a dynamic Collector, and GoldenGate users generally do not interact with it. However, you can run Collector manually. This is known as a static Collector.
- Not all GoldenGate configurations use a Collector process.When a dynamic Collector is used, it can receive information from only one Extract process,so there must be a dynamic Collector for each Extract that you use. When a static Collector is used, several Extract processes can share one Collector. However, a one-to-one ratio is optimal.
- The Collector process terminates when the associated Extract process terminates.By default, Extract initiates TCP/IP connections from the source system to Collector on the target, but GoldenGate can be configured so that Collector initiates connections from the target. Initiating connections from the target might be required if, for example, the target is in a trusted network zone, but the source is in a less trusted zone.