What happens when the Capture or Integrate process is stopped for any reason, will the replication process catch up once it has been restarted?

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    ggoodrich
    Keymaster

    HVR has internal recovery algorithms so that, when an HVR process is killed and restarted, it will always start again at the correct point. So there is no risk of losing data or duplicated changes due to HVR crashes.
    However, with Log based capture, there is a related issue that must be considered:
    The retention of the database log files (Ingres journal files or Oracle archive files). When the capture job is stopped for some time it needs to revert to the Ingres journal files / Oracle archive files because the transaction log files (redo logs) are already overwritten. E.g. when the capture job is stopped yesterday and these files are thrown away each night, the capture job will fail when it is restarted today because it can not find the correct point in the available files. To recover from this the channel needs to be reinitialized using HVR Load followed by an HVR Refresh.
    There are two ways of avoiding this:

    1. Keep the DMBS log files (e.g Oracle archive files) available for a couple days. When the capture job has not run for a couple of days probably you would reinitialize the channel anyway.
    2. Use hvrlogrelease: A script that can be run from the crontab that makes private copies (hard-links) of the files that still might be needed be HVR. See hvrload.
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