> > > IIRC _db_file_exec_read_count=8 and > _db_file_optimizer_read_count=((max I/O size)/DB_BLOCK_SIZE)), so > usually 1MB I/O size. I think you mean _db_file_optimizer_read_count=8 and _db_file_exec_read_count = ((max I/O size)/DB_BLOCK_SIZE)). This is a reasonable assumption, but I'm not sure how Oracle determines the maximum I/O size. On my laptop, Oracle 10.2.0.1 and 11.1.0.6 show quite different _db_file_exec_read_count. In 10.2.0.1 : _db_file_exec_read_count = 5 In 11.1.0.6 : _db_file_exec_read_count = 128 It seems quite dependent on Oracle version, not just on OS and/or storage settings. ================================ Dion Cho - Oracle Performance Storyteller http://dioncho.wordpress.com (english) http://ukja.tistory.com (korean) ================================