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Block Size

The size of the block cursor used for find operations on the table.

Supported By

DataFlex SQL Drivers (SQL Server, DB2, and ODBC), revision 5 and higher

Value

2..

Associated Attribute

DF_FILE_BLOCK_SIZE

Remarks

The SQL drivers use database cursors to access data. For every table, two database cursors may be created:

  • A single row cursor for find equal operations
  • A block cursor for every other find operation

Block cursors will fetch multiple rows when retrieving data. The default value is 10 (rows).

Using block cursors speeds up find operations and creates a form of caching. The driver retrieves multiple records at a time, and the next record will be fetched from memory rather than from the back end. However, using a cache introduces the risk of returning incorrect data.

To mitigate this risk, a find cache timeout can be set (in milliseconds). If the time between two find operations exceeds the find cache timeout (default is 10 milliseconds), the driver will fetch the data from the back end even if not all records in the cache have been processed. The find cache timeout can be configured using the Find_Cache_Timeout driver configuration keyword.

See Also