Set CacheSize to control how many rows the ADO dataset’s provider keeps cached in its buffer and how many to retrieve at one time into local memory. Default value of CacheSize is 1 and the minimum allowed value is 1. 

For example, if CacheSize is set to 20, when the dataset is first activated the associated provider retrieves the first 20 rows into local memory. As the row pointer is moved through this recordset, the provider retrieves the data from the local memory buffer. If the dataset’s row pointer moves beyond the last of these 20 buffered rows, the provider retrieves the next 20. 

CacheSize represents the maximum number of rows to retrieve at one time. If the number of rows remaining to be retrieved is less than CacheSize, the remaining rows are retrieved and no exception is raised. The number of rows that can be returned by the provider can be less than all of the rows if the ADO dataset component’s MaxRecords property is set to other than the default (all rows).

BlockReadSize 

MaxRecords