Prepared statements and Cursors.Single connection may have many prepared statements and cursors. Their number finally can be limited but each of them still can have very large memory consumption.

• 准备查询语句以及游标。单次链接可能会有很多的准备好的语句以及游标。它们的数量最后可以限定,但是仍然会消耗大量的内存。