The data flow task in SSIS sends data in series of buffers. The data one buffer hold is bounded by Default BufferMaxRows and DefaultBufferMaxSize, two Data Flow properties. They have default values of 10,000 and 10,485,760 (10 MB). That means, one buffer
will contain either 10,000 rows or 10 MB of data, whichever is less. You can adjust these two properties based on your scenario. Setting them to a higher value can boost performance, but only as long as all buffers fit in memory.
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Indeed we did have a filter on a specific GUID primary key. We've since reworked the datasync on the specific database that was receiving the issue and are no longer encountering it. Running the query now yields: 27590. Thank you for the
information, we'll keep an eye on it for the future.