number of large i/o buffers

number of large i/o buffers sets the number of allocation unit-sized buffers reserved for performing large I/O for certain SAP ASE utilities.

Summary Information

Default value


Valid values




Display level


Required role

System administrator

Configuration groups

Disk I/O, Memory Use, SQL Server Administration

These large I/O buffers are used primarily by the load database command, which uses one buffer to load the database, regardless of the number of stripes it specifies. load database then uses as many as 32 buffers to clear the pages for the database it is loading. These buffers are not used by load transaction. To perform more than six load database commands concurrently, configure one large I/O buffer for each load database command.

create database and alter database use these buffers for large I/O while clearing database pages. Each instance of create database or load database can use as many as 32 large I/O buffers.

These buffers are also used by disk mirroring and by some dbcc commands.

Note: In SAP ASE version and later, the size of the large I/O buffers is one allocation (256 pages), not one extent (8 pages). The server thus requires more memory allocation for large buffers. For example, a disk buffer that required memory for 8 pages in earlier versions now requires memory for 256 pages.