Microsoft KB Archive/65469

= LAN Manager 2.x DISK01.SYS Information =

Article ID: 65469

Article Last Modified on 11/15/1999

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APPLIES TO


 * Microsoft LAN Manager 2.2c

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This article was previously published under Q65469



SUMMARY
The file BASEDDnn.SYS, where &quot;nn&quot; is 01 for ISA and EISA (non-ABIOS) machines, and 02 for PS/2 MCA (ABIOS) machines, is located in the root directory of the primary partition. This file is the default driver file for the clock, screen, disk driver, etc., and is limited to a 64K file size. Adding specific device drivers such as DISKnn.SYS, KBDnn.SYS, etc., allows you to work around the 64K file size limit, and also adds functionality that is missing in BASEDDnn.SYS. These files are also placed in the root directory.

OS/2 LAN Manager version 2.00 offers to install a DISKnn.SYS file to add functions that are not supported in BASEDDnn.SYS. The DISKnn.SYS file is part of OS/2 and is not on the OS/2 LAN Manager disks. Compaq OS/2 version 1.21 automatically installs this file during its installation and then OS/2 LAN Manager does not also need to install this file. The OS/2 LAN Manager setup program will, however, still offer to install this file. Two important functions in DISKnn.SYS used by OS/2 LAN Manager are fault tolerance and a disk read/write technique called &quot;scatter gather.&quot; DISKnn.SYS supports fault tolerance when it is enabled with some ring 3 utilities and interfaces to the DISKFT.SYS driver. HPFS386, the file system packaged with OS/2 LAN Manager, uses the enhanced device driver interface called &quot;scatter gather.&quot; This interface allows multiple requests to be chained together and passed to the driver all at once, which saves the overhead of calling the driver multiple times.

In addition, within each request, there is the capability to specify a list of separate memory areas to be used for the target of the read or write operation. Together, the list of memory areas and the multiple requests allow the file system to pass a single packet to the device driver that handles discontiguity on the disk media, and discontiguity in memory.

HPFS386 does not require that this interface to the disk driver be supported, rather it will use it if it is there. HPFS386 will function without the use of DISKnn.SYS. OS/2 LAN Manager also functions without DISKnn.SYS but will use the extra functionality if it is installed.

Additional query words: 2.00 2.10 2.10a 2.20

Keywords: KB65469

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