Data Recovery

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This topic explains auto and manual data recovery.

Note: It is recommended that the collector for which the data recovery is intended is in the same time zone as the server. If there is a mismatch, there is a possibility that data recovery will be incomplete.

Auto Data Recovery

When the auto recovery logic is executed, the collector first determines how long it has been since the last write. It compares the current time to data in the registry key LastSampleWriteTime, which stores the last time data was written to the archive. The collector compares this to the Max Recovery Time that is specified in the user settings and performs a raw data query on the shorter of these two periods. Then it takes the shorter of these two and do a raw data query for all tags. It then processes the returned samples in sequential order based on time.

For example, if the collector was shut down for 8 hours, but Max Recovery Time was 4 hours, only 4 hours of data would be recovered.

Recovery logic places an end-of-collection marker at the point in time where the collector was shut down. This end-of-collection marker may or may not be there once the recovery is complete. As part of recovery logic, if recovery data point time exactly at that timestamp where the end-of-collection marker is there, then it is overwritten with the recovered good data.