Microsoft KB Archive/106121

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Article ID: 106121

Article Last Modified on 10/31/2006

This article was previously published under Q106121


LAN Manager servers may fail or "sleep" under extreme operating stress, refusing to initiate new sessions while allowing active sessions to continue for a while. Three problems cause the following stress-related symptoms:

  • SCSI bid time-out failures
  • Kernel failures
  • NETAPI.DLL or SCSI bid time-out problems

This article discusses these three problems and several other topics in this order:

  • Causes of Server Stress
  • Server-Stress-Related Problems
  • Non-Server-Stress-Related Problems
  • Problem 1: SCSI Bid Time-out Failures
  • Problem 2: Kernel Failures
  • Problem 3: NETAPI.DLL or SCSI Bid Time-out Problems
  • Procedures for Installing the Fixes
  • Configuration (of servers prone to these problems)
  • Tuning Recommendations
  • Utilities and Diagnostics

Each problem section is organized in the standard style: Symptoms, Cause, Resolution/Workaround.

You can obtain Microsoft OS/2 LAN Manager updates from Microsoft PSS, Corporate Network Systems. Fixes are scheduled for inclusion in the LAN Manager 2.2b Patch.



Several system conditions can create server stress: a large number of workstations with active sessions accessing the file server, or problems with foreground processes such as ring 3 services (SQL Server, the NetLogon service, and backup operations).


Stress failures can disrupt some server processes while other OS/2 processes continue unaffected. Even when critical ring 0 or kernel-level failures affect the server, trap error messages are not always displayed on the server monitor or through an OS/2 kernel debugger, and some OS/2 processes can continue to operate for a while (for instance, the HPFS386 cache and operations serviced by it) although the Program Manager cannot be accessed and keyboard input is not responded to.


Complete server hangs are often caused by something other than sleeping servers:

  • System CPU hardware failures that hang the server and require a cold boot.
  • A system device or ring 0 device driver that shuts down interrupts and does not re-enable them, locking the server and stoppping response to keyboard I/O
  • Network adapters that halt all server processing.
  • A tight I/O-bound application loop such as a process that continuously writes to the screen, starving other processes on the server. If a process remains at high priority in a PM screen group, it blocks other processes. It is a good idea to avoid running local processes involving continuous screen or other device I/O on an OS/2 LAN Manager file server. Run only specifically designed server applications, and avoid running applications such as tape backup software during peak hours.


Sleeping or comatose server; disk access blocked.


There are many possible symptoms. When a SCSI bid time-out occurs for disk drive requests, drive access is blocked even though network I/O does not stop and users can connect to the server by the NET USE or NET ADMIN commands. If primary disk drive access is blocked and SWAPPER.DAT is located there, local OS/2 foreground processes may become inaccessible, the system may not respond to keyboard input, and Task Manager may fail. No operation can write to the blocked disk drive. Only operations serviced by HPFS386 cache continue to operate. A PSTAT listing reveals all processes blocked except those serviced by cache.

If server performance falls, access to CD-ROM drives may fail if time-outs occur. Attempting to access a logical drive letter from the server console associated with a CD-ROM hangs that OS/2 screen group. Also, if multiple CD-ROM devices containing large amounts of data are attached to the server, this failure can result in a sleeping server hang:

   Net start server
   The server is starting.....................................

The server slows or halts. CPU utilization increases and workstations receive poor server response.

Servers with a NETAPI.DLL failure respond to console keyboard commands. Using the servers' workstation service allows network access to other servers by means of NET USE for users logged on at the server. Because a NETAPI.DLL failure leads to a NetLogon service failure, users cannot log on if the server is a domain controller. PSTAT may also reveal a NetLogon announcer thread failure if it becomes stuck in a critical section.

If the server is experiencing SCSI bid time-outs and disk access is blocked, the server service degrades gradually. As long as an HPFS386 server is servicing requests from cache, it maintains existing sessions. For new sessions, NetBIOS session-alive traffic remains active but workstations cannot connect to the server. Before long, the only continuing traffic is LLC, NetBEUI low-level transport operations.

Both NETAPI.DLL and SCSI bid time-out failures can cause the ring 3 server scavenger thread to fail. Workstations attempting new connections receive error 51. Error 53 is sometimes returned, but this actually is error 51 erroneously reported by LAN Manager. Likewise, error net3779, sometimes returned to users attempting to log on to a sleeping primary domain controller (PDC), is incorrect and should be reported as error 51. No new listens are posted by the ring 3 server, Netservr Scavenger thread. Net session at the server reports existing sessions, but the ring 3 server revokes new requests.

Possible error messages:

Error 51: The remote computer is not available.
Error 53: The network path was not found.
Error 240: The network connection is disconnected.
Net3779: Your logon attempt has failed due to an incorrect user name or password.

Attempting to shut down the server may return the following messages:

Net Stop Server
Net2190: The service ended abnormally

Net Stop Workstation
Net2189: The service cannot be controlled in its present state
OS/2 shutdown may cause the server to hang.


This often is caused by a lack of time-out handling code in the OS/2 bid, which in turn causes disk requests to time-out due to server stress and slow responses from I/O devices. Requests (called RCBs) are passed through the file system to the SCSI bid through IOS$, which provides I/O access to the bid from file systems. The requests include time-out values. For SCSI bids, this value is passed as a SCSI request block (SRB) parameter for time-out. Time-outs cannot be handled properly unless the bid monitors the SRB time-out value for all I/O queues. If a request expires, you should reset the SCSI bus and I/O queue time-outs, and let operations retry. If operations are not allowed to retry, threads involved with the I/O process hang.

Certain hardware components and data transfer quantities can cause or contribute to these problems:

  • Slow SCSI devices
  • Multiple devices
  • Multiple large hard-disk drives
  • Multiple tape drives
  • CD-ROM drives

Some kernel memory-management routines for CSD5050 and subsequent revisions have been updated from 286-specific code to 386-specific code. Memory compaction on a 386 does not take advantage of the 386 processor double word capability, resulting in poor performance, especially with memory- intensive operations. Primary domain controller ring 3 server threads can hang if a backup domain controller causes a semaphore deadlock by calling NetAccountSync(). The symptoms indicate that the ring 3 server Scavenger thread has failed. If the ring 3 server fails, active sessions continue operating but new connections are refused. The scavenger thread also checks disk drives for free space, and hangs if a SCSI bid time-out failure occurs while the check is in progress. The ring 3 server (Netservr) provides all file services for FAT partitions only. On an OS/2 LAN Manager HPFS386 server, only new server connection requests are handled by the ring 3 server. The ring 0 HPFS386 server is optimized for performance, and it--not the ring 3 server--handles file service. As a result, if the ring 3 server fails, HPFS386 continues to service requests although new connections are refused and the server appears to sleep.


Update SCSI bids to address the lack of time-out code. Following are instructions for current SCSI bids divided into four classes.

A. SCSI controller bids for which updates are available
B. SCSI controller bids without time-out handling code that can be replaced with monolithic drivers
C. SCSI controller bids without time-out handling code or currently available monolithic drivers
D. SCSI bids with time-out code and shipped in OS/2 1.301 LAN Manager 2.2.

A. SCSI controller bids for which updates are available:

  • COMPAQ Cpq710 bid *
  • UltraStor Ultra24 bid *
  • Adaptec 174x bid

  • installed as BOOTBID.BID, not preinstalled with OS/2 LAN Manager; these will not be included in LAN Manager 2.2b

Updates are available from Microsoft PSS, and on the PSS internet server in Bussys\LANMAN\UNSUP-ED (see GOWINNT.MICROSOFT.COM). Use FTP to get the files. B. SCSI controller bids without time-out handling code which can be replaced with monolithic drivers:

  • IBM PS/2 ABIOS.BID (Replace with OS/2 1.3 CSD5050 or later drivers)
  • COMPAQ CPQARRAY BID (Replace with OS/2 1.21 or later drivers)

To work around the problem, replace these with monolithic drivers. Monolithic drivers do not support LADDR-specific features such as FT or CdRomIfs, but proper time-out code is available for hard disk drives. NOTE: Monolithic drivers have not been certified or exhaustively tested with OS/2 1.301 CSD5015 LAN Manager 2.2.

C. SCSI controller bids without time-out handling code or currently available monolithic drivers:

  • Adaptec 154X and 164X
  • Future Domain WD7000EX and FD16-700 bids
  • Dell001 bid

To work around the problem, install an adapter and driver that support time-outs until the manufacturer provides a fix.

D. SCSI bids with time-out code and shipped in OS/2 1.301 LAN Manager 2.2:

  • ESDI-506 bid used for IDE, ESDI, and WD ST-506 compatible controllers
  • DPT201X bid
  • NCRC700, NCRC710 and NCRC90


Server slows down (OS2KRNL). Update the OS/2 kernel and redirector using the following:

   OS2KRNL           OS2 1.301 CSD01.001
   NETWKSTA.SYS      LM22 CSD00.013


Server rejects new sessions. (NETAPI.DLL, SCSI bid, or resource problems). Update NETAPI.DLL and NETLOGON.EXE CSD00.036. Following are procedures for installing the fixes on a LAN Manager 2.2 OS/2 1.301 server:


NOTE: The fixes provided have not yet been released as part of an OS/2 LAN Manager update. As a result, they have not been subjected to exhaustive release testing. Please test the fixes prior to implementing them on a production server to assure that the fixes operate properly.

Procedure 1: Installing OS2KRNL

  1. From the OS/2 File Manager, do the following:

    1. Select these options:

      • View
      • Include
      • All File Flags (Hidden)
      • Set View
      • Select OS2KRNL
      • File
      • Change Flags
    2. Cancel the selection of these options:

      • System
      • Hidden
      • Read Only
  2. Issue a NET STOP command on the workstation.
  3. Shut down the server from the OS/2 desktop.
  4. Use an HPFS386 recovery disk to boot the server.
  5. Use OS/2 Disk 1 to perform the following command:

    chkdsk c: /f:386

  6. Issue the following commands:

    rename c:\OS2KRNL c:\OS2KRNL.old
    rename c:\lanman\netprog\netwksta.sys *.old
    copy a:\netwksta.sys c:\lanman\netprog

  7. Restart the server.

Procedure 2: Installing monolithic drivers on a LAN Manager 2.2 OS/2 1.301 server

  1. In the root directory, issue the following commands:

    md laddr
    copy *.sys laddr (EXCEPT CONFIG.SYS)
    copy *.bid laddr
    copy *.tsd laddr
    copy *.vsd laddr

  2. Copy the following files from OS/2 1.21 or 1.3 installation Disk 1 (ISA computers) or Disk 2 (PS/2--Micro Channel computers) to the root directory


    where X = 1 for ISA computers and 2 for PS/2--Micro Channel.
  3. Rem out the lines in the CONFIG.SYS file from DEVICE=DENON.VSD to IFS=CDROM.IFS.
  4. Reboot the machine.

Procedure 3: Installing updated NETAPI.DLL and NETLOGON.EXE

  1. Type the following and press ENTER:

    copy c:\config.sys c:\config.sav

  2. Make this TEMPORARY change to the CONFIG.SYS file:

    E Config.sys
    (remove c:\lanman\netlib)

  3. Shut down the server.
  4. Restart the server.
  5. Issue the following commands:

    rename c:\lanman\netlib\netapi.dll c:\lanman\netlib\netapi.old
    copy a:\netapi.dll c:\lanman\netlib
    rename c:\lanman\services\netlogon.exe c:\lanman\services\netlogon.old
    copy a:\netlogon.exe c:\lanman\services
    copy c:\config.sav c:\config.sys


Common configuration for servers exhibiting "sleeping" problems:

  • 486 (> 33 mhz) PC server
  • SCSI controller or IDE controller (16-bit ISA or 32-bit EISA or MCA)
  • LAN Manager 2.1, 2.1a, 2.2
  • Microsoft OS/2 1.301
  • HPFS386 partitions
  • Primary domain controller operation NetLogon service
  • Ifs ...... /cache:4096 or larger cache size
  • OS/2 ring 3 applications such as NetLogon or SQL Server


Check the server error log for the following error

Net3101: The system ran out of a resource controlled by the *** option

where *** is the numbigbuf or numreqbuf parameter.

   Numbigbuf = x    (1-80)
   Numreqbuf = x    (1-300)

If you find this error, edit LANMAN.INI and increase the corresponding parameters to correct the problem and prevent future server failures. LAN Manager allocates request and big buffers statically at server startup. Under high-stress operating conditions, these resources can be depleted, causing the ring 3 server threads (including the Scavenger) to fail.


PSTAT: PSTAT reports made before or after the failure verify that one or more NetLogon threads became stuck in a critical section, or Netservr threads, including the Scavenger thread, have been terminated.

Process and Thread Information on a sample PSTAT screen:

Process   Thread
Name       ID    Priority   Block ID   State
NETLOGON   04      06FF     00000000  CritSec

Sniffer protocol analyzer traces will reveal that the server has no listen commands outstanding. As the workstation repeatedly fails to connect, it receives this packet and returns error 51 to the user.

Sample detail of a Sniffer screen:

                        - Frame 1 -
   SUMMARY  Delta T     Destination   Source        Summary
   M        1           Workstation   Server  NETB Name Server
   NETB: ----- NETBIOS Name Recognized -----
   NETB: Header length = 44, Data length = 0
   NETB: Delimiter = EFFF (NETBIOS)
   NETB: Command = 0E
   NETB: No LISTEN command outstanding for this name.
   NETB: Caller's name type = 00 (Unique name)
   NETB: Transmit correlator = 000D
   NETB: Response correlator = 0000
   NETB: Receiver's name = Workstation<00>
   NETB: Sender's name = Server

If the SCSI bid time-out failures occur, then HPFS386 will stop providing SMB service if the request cannot be serviced from cache. Sessions are eventually dropped and only LLC and NETB traffic remain active. The NETB traffic may eventually end as well.

Sample from a Sniffer summary report:

    98    0.0369  SERVER        WORKSTATION   SMB C Open  \test.cmd
    99    0.0429  WORKSTATION   SERVER        NETB D=68 S=05 Data ACK
   100    0.0011  SERVER        WORKSTATION   LLC R D=F0 S=F0 RRNR=117
   101   15.5651  SERVER        WORKSTATION   NETB Session alive
   102    0.2152  WORKSTATION   SERVER        LLC R D=F0 S=F0 RR NR=36
   103    2.0314  WORKSTATION   SERVER        NETB Session alive
   104    0.0008  SERVER        WORKSTATION   LLC R D=F0 S=F0 RRNR=118

Additional query words: sleeping, 51 2.00 2.0 2.10 2.1 2.10a 2.1a 2.2 2.20

Keywords: KB106121