The size of large I/O disk buffers used by create database, alter database, load database, and dbcc checkalloc to issue multiple parallel I/O is now one allocation, (256 pages), not one extent (8 pages). This increase means that the server requires more memory allocation to issue large buffers. The server now requests that more memory be configured, but this memory is not allocated until a command requests large I/O buffers. A disk buffer that required memory for 8 pages in earlier versions now needs memory for 256 pages. The limit on the configuration parameter number of large io buffers, with a default value of 6, has increased from 32 to 256. At the same time, the internal limit on the number of large I/O buffers a single command can create has been increased from 8 to 32. These increases allow you to both create larger buffers, and use more buffers per command. Whatever value you assign to the configuration parameter dynamic allocation on demand, memory for large I/O buffers is always allocated on demand. This memory pool is shrinkable: if the number of large I/O buffers decreases, memory requirements per buffer decrease accordingly.
