private Scn calculateEndScn(OracleConnection connection, Scn startScn, Scn prevEndScn) throws SQLException {

    .....

    Scn currentScn = archiveLogOnlyMode? getMaxArchiveLogScn(currentLogFiles)
        : connection.getCurrentScn(); streamingMetrics.setCurrentScn(currentScn);

    // Add the current batch size to the starting system change number
    final Scn currentBatchSizeScn = Scn.valueOf(streamingMetrics.getBatchSize());
    Scn topScnToMine = startScn.add(currentBatchSizeScn);

    // Control adjusting batch size
    boolean topMiningScnInFarFuture = false;

 

   // this condition mathematical expresion as below show

    topScnToMine - currentScn >currentBatchSizeScn

    because topScnToMine = startScn + currentBatchSizeScn

    so  this condition will become startScn - currentScn > 0

    it's always false. we need compare it with defaultBatchSize

    if (topScnToMine.subtract(currentScn).compareTo(currentBatchSizeScn) > 0)

   

{                 streamingMetrics.changeBatchSize(false, connectorConfig.isLobEnabled());         topMiningScnInFarFuture = true;     }

    }

    // same reason, we need compare it wih defaultBatchSize

    if (currentScn.subtract(topScnToMine).compareTo(currentBatchSizeScn) > 0)

{         streamingMetrics.changeBatchSize(true, connectorConfig.isLobEnabled());     }

......

}

 

 

The reason is:

 

1. topScnToMine.subtract(currentScn).compareTo(currentBatchSizeScn) > 0 result always is false, because topScnToMine = startScn.add(currentBatchSizeScn), so while currentBatchSizeScn increment at max will nevent reduce. it is a issue, need to fix.

1. currentScn.subtract(topScnToMine).compareTo(currentBatchSizeScn) > 0 change to compare with default reason is that i think if currentScn - topScnToMine = currentBatchSizeScn meaning lag is increasing, even if we can catch up to currenScn next time. if compare with defaultBatchSize, in the worst case there is only a lag of defaultBatchSize size.