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Compaq TCP/IP Services for OpenVMS

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20.10.7 Restoring a Container File System

For a typical image restore, follow normal OpenVMS procedures.

For a nonimage restore, an additional step is required after the restore. The Files--11 file identifiers are recorded in the container file. These must be updated by the TCP/IP management command ANALYZE CONTAINER /REPAIR.

This extra step is also required for an image restore if the save set is being restored with the /NOINITIALIZE qualifier to a volume with a different label or if it is being restored to a bound volume set that has a member that was added since the time of the image backup.

20.11 Setting Up NFS Security Controls

The NFS server and the OpenVMS operating system provide many levels of security controls you can use to protect your file systems. Section 20.1.3, Section 20.1.4, and Section 20.1.7 describe how the server uses the proxy and export databases to restrict client access, and how to use OpenVMS account privileges and file protections to control access to files and directories.

The NFS server provides additional security controls through the use of the noproxy_enabled attribute. You can set this attribute in the NFS server site-specific startup file SYS$STARTUP:TCPIP$NFS_SERVER_SYSTARTUP.COM.

The server uses this attribute while it is running. If the attribute is set, a proxy is not required for users attempting to access the NFS server. For more information about the NFS server attributes, see Table 20-3.

20.12 Modifying NFS Server Attributes

You can modify the way the NFS server works by specifying NFS server attributes using the SYSCONFIG command. The characteristics of the NFS server that you can modify include:

  • Proxy security
  • Default proxy UID
  • Default proxy GID
  • Maximum concurrent TCP threads
  • Maximum concurrent UDP threads

To make permanent modifications:

  1. If it does not already exist, create the file SYS$STARTUP:TCPIP$NFS_SERVER_SYSTARTUP.COM.
  2. Include the SYSCONFIG command to set the variables. For example:

    $ SYSCONFIG -r nfs_server tcp_threads=20 udp_threads=40
  3. Shut down and then restart the NFS server to make the changes take effect. For example:


Future upgrades or installations will not overwrite the definitions in the TCPIP$NFS_SERVER_SYSTARTUP.COM file.

Modifying NFS server characteristics can affect NFS server performance. Be sure you understand the impact (review Section 20.15) before making any changes.

Table 20-3 describes the NFS server attributes.

Table 20-3 Modifying NFS Server Attributes
Attribute Description
noproxy_enabled Enables the use of the noproxy_uid and noproxy_gid attributes. If this attribute is not set to 1, proxies are required for server access.

If the value is 0, files owned by a user that is not in the proxy database are assumed to be owned by UID=-2/GID=-2. If the value is 1, files owned by a user not in the proxy database are reported to be owned by the values of the noproxy_uid and noproxy_gid attributes.

noproxy_uid Specifies the default UID when a user cannot be translated by the proxy.
noproxy_gid Specifies the default GID when a user cannot be translated by the proxy.
tcp_threads Specifies the number of concurrent TCP threads within the server. A value of zero will disable the TCP protocol.
udp_threads Specifies the number of concurrent UDP threads within the server. This value must not be zero.
vnode_age Specifies the number of seconds in the time interval since the last file access request.

The server keeps an activity timestamp for each opened file to help manage the open file cache. You can also modify this value with the /INACTIVITY qualifier to the SET NFS_SERVER command.

The default setting for this variable is 120, or 2 minutes. Be careful not to set this value to a small interval; this might reduce performance.

20.13 Modifying File System Characteristics

The file SYS$STARTUP:TCPIP$NFS_SERVER_STARTUP.COM also defines a set of logical names that set the file system parameters. Table 20-4 describes these logical names.

Table 20-4 File System Logical Names
Logical Name Description
TCPIP$CFS_CACHE_LOW_LIMIT Defines the minimum size of the free buffer list. When the list is smaller than the value of this logical name, the file system starts to reclaim used buffers.

The default is 4 buffers.

The free buffer list needs at least 4 free buffers (not taken by cache). If the actual number of free buffers is less than TCPIP$CFS_CACHE_LOW_LIMIT, the used buffers are returned to the free list until the size of the free list reaches the value of TCPIP$CFS_CACHE_HIGH_LIMIT.

TCPIP$CFS_CACHE_HIGH_LIMIT Defines the number of buffers the file system tries to keep in the free buffer list.

The default is 8 buffers. See TCPIP$CFS_CACHE_LOW_LIMIT.

In a busy server environment, setting this parameter higher is likely to improve performance.

TCPIP$CFS_CACHE_SIZE Defines the maximum number of cache buffers to be allocated.
TCPIP$CFS_TRANSFERSIZE Defines the optimum size (in bytes) of the data transferred between server and client on READ and WRITE operations.

The default is 8K bytes (8192 bytes). This value is used in most NFS server implementations.

TCPIP$CFS_SHOW_VERSION Sets the SHOW_VERSION logical name ON or OFF. If ON, the NFS server returns to the client file names with version numbers, even if there is only one version of the file.

The default is OFF.

TCPIP$CFS_MODUS_OPERANDI Defines various operating modes. Use only under the advice of your Compaq support representative.
TCPIP$CFS_FATAL_MESSAGES Defines the terminal device to which the important error messages are directed, in addition to the normal error messages that are sent to the operator's console.

The default is _OPA0:.

20.14 File Locking

TCP/IP Services supports a partial implementation of NFS network locking, which allows users to lock files. The software coordinates locks among remote users and between remote and local users. The file locking features is applicable regardless of whether the OpenVMS Record Management Services (RMS) is used. However, NFS does not coordinate network locking and RMS record locks.


This version of NFS does not support byte-range locking. If a byte-range lock request is received, it is handled as a file lock request.

File locking is implemented using the Network Lock Manager (NLM) (also known remote procedure call, or RPC, lockd ) and the Network Status Monitor (NSM) (also known as RPC statd ). The NLM coordinates locks made by clients. The NSM recovers lock information in case the server or client fails. The NSM uses the NLM to keep the host list when the client or the server fails and reboots, as follows:

  • If the client fails and reboots, it notifies the NSMs on its host list. In turn, the NSMs tell their local NLMs to free any locks held for that client.
  • If the server fails, when it reboots it notifies the NSMs on each client host in its host list. In turn, the client NSMs tell their local NLMs to request again all the locks that were granted on their behalf by the server before it failed.

The NSM and the NLM are enabled if you select LOCKD/STATD in the TCPIP$CONFIG.COM configuration procedure. As a result, two processes are started when you start TCP/IP Services: TCPIP$LOCKD and TCPIP$STATD. The NLM can be configured with the following optional parameters:

  • TCPIP$LOCKD_TIMEOUT_PERIOD specifies the timeout period (in seconds). This value defines the amount of time for the client to wait before retransmitting a lock request to which the server has not responded. The default setting is 5 seconds.
  • TCPIP$LOCKD_GRACE_PERIOD specifies the grace period (in seconds). This value defines the amount of time the NLM will deny new lock requests after a failure while the NSM is recovering the lock status. The default setting is 15 seconds.

To set these parameters, create or edit the following file:


20.14.1 File Locking Service Startup and Shutdown

The file locking services can be shut down and started independently of TCP/IP Services. This is useful when you change parameters or logical names that require the service to be restarted.

The following files are provided:

  • SYS$STARTUP:TCPIP$LOCKD_STARTUP.COM allows you to start up the LOCKD component independently.
  • SYS$STARTUP:TCPIP$STATD_STARTUP.COM allows you to start up the STATD component independently.
  • SYS$STARTUP:TCPIP$LOCKD_SHUTDOWN.COM allows you to shut down the LOCKD component independently.
  • SYS$STARTUP:TCPIP$STATD_SHUTDOWN.COM allows you to shut down the STATD component independently.

To preserve site-specific parameter settings and commands, create the following files. These files are not overwritten when you reinstall TCP/IP Services:

  • SYS$STARTUP:TCPIP$LOCKD_SYSTARTUP.COM can be used as a repository for site-specific definitions and parameters to be invoked when the LOCKD component is started.
  • SYS$STARTUP:TCPIP$LOCKD_SYSHUTDOWN.COM can be used as a repository for site-specific definitions and parameters to be invoked when the LOCKD component is shut down.

20.15 Improving NFS Server Performance

This section provides information to help you identify and resolve problems and tune system performance.

20.15.1 Displaying NFS Server Performance Information

The SHOW NFS_SERVER command displays information about the running NFS server. You can use the information to tune NFS server performance.

You can enter SHOW NFS_SERVER for a specific client or host if it is listed in the proxy database. The counter information can be especially useful in determining the load on your system.

For more information about the SHOW NFS_SERVER command, refer the Compaq TCP/IP Services for OpenVMS Management Command Reference.

20.15.2 Displaying File System Information

The SHOW CFS command is useful for monitoring the distribution of the file system services and the consumption of system time by the various system services. See the Compaq TCP/IP Services for OpenVMS Management Command Reference manual for a detailed description of the SHOW CFS command.

20.15.3 Increasing the Number of Active Threads

The NFS server is an asynchronous, multithreaded process. This means that multiple NFS requests can be processed concurrently. Each NFS request is referred to as a thread. With increased server activity, client users may experience timeout conditions. Assuming the server host has the available resources (CPU, memory, and disk speed), you can improve server response by increasing the number of active threads. You do this by changing the value for the appropriate NFS server attributes, as described in Section 20.12.

The NFS server supports both TCP and UDP connections. You can control the maximum number of concurrent threads for each type of connection.

  • To set the maximum number of TCP threads, set the tcp_threads attribute.
  • To set the maximum number of UPD threads, set the udp_threads attribute.

Do not set the UDP maximum threads to zero. If you set the variable to zero, the protocol will be disabled.

If you increase the number of active threads, you should also consider increasing the timeout period on UNIX clients. You do this with the /TIMEOUT option to the TCP/IP Services MOUNT command.

If your clients still experience timeout conditions after increasing the number of active threads and the timout period on the client, you may need to upgrade your hardware.

20.15.4 OpenVMS SYSGEN Parameters That Impact Performance

The following OpenVMS SYSGEN parameters impact NFS server performance:

    The CHANNELCNT parameter sets the maximum number of channels that a process can use. Ensure that CHANNELCNT is set large enough to handle the total number of files accessed by all clients.


    The NFS server process is also limited by the FILLM of the TCPIP$NFS account's SYSUAF record. The effective value is the lower of the FILLM and CHANNELCNT values.
  • ACP parameters
    The NFS server issues a large number of ACP QIO calls through CFS. Altering certain ACP parameters could yield better performance. If you have reliable disks, you may want to set the parameter ACP_DATACHECK to zero to avoid extra disk I/Os. Directory searching and file attribute management constitutes a majority of the ACP operations. Therefore, Compaq recommends that you increase parameters such as ACP_HDRCACHE, ACP_MAPCACHE, ACP_DIRCACHE, ACP_FIDCACHE, and ACP_DATACACHE.
  • LOCK parameters
    The various lock manager parameters may need some alteration because CFS uses the lock manager extensively. A lock is created for each file system, each referenced file, and each data buffer that is loaded into the CFS cache.

    Maximum virtual size of a process in pages. The NFS server requires larger-than-normal amounts of virtual address space to accommodate structures and buffer space.
    Maximum physical size of a process in pages. The larger the working set, the more pages of virtual memory that can remain resident. Larger values reduce page faults and increase the server's performance.

Chapter 21
NFS Client

The Network File System (NFS) client software enables client users to access file systems made available by an NFS server. These files and directories physically reside on the remote (server) host but appear to the client as if they were on the local system. For example, any files accessed by an OpenVMS client --- even a UNIX file --- appear to be OpenVMS files and have typical OpenVMS file names.

This chapter reviews key concepts and describes:

For information about the NFS server, see Chapter 20.

21.1 Key Concepts

Because the NFS software was originally developed on and used for UNIX machines, NFS implementations use UNIX file system conventions and characteristics. This means that the rules and conventions that apply to UNIX file types, file names, file ownership, and user identification also apply to NFS.

Because the TCP/IP Services NFS client runs on OpenVMS, the client must accommodate the differences between the two file systems, for example, by converting file names and mapping file ownership information. You must understand these differences to configure NFS properly and to successfully mount file systems from an NFS server.

The following sections serve as a review only. If you are not familiar with these topics, see the DIGITAL TCP/IP Services for OpenVMS Concepts and Planning guide for a more detailed discussion of the NFS implementation available with the TCP/IP Services software.

21.1.1 NFS Clients and Servers

NFS is a client/server environment that allows computers to share disk space and users to work with their files from multiple computers without copying them to the local system. Computers that make files available to remote users are NFS servers. Computers with local users accessing and creating remote files are NFS clients. A computer can be an NFS server or an NFS client, or both a server and a client.

Attaching a remote directory to the local file system is called mounting a directory. A directory cannot be mounted unless it is first exported by an NFS server. The NFS client identifies each file system by the name of its mount point on the server. The mount point is the name of the device or directory at the top of the file system hierarchy. An NFS device is always named DNFSn.

All files below the mount point are available to client users as if they reside on the local system. The NFS client requests file operations by contacting a remote NFS server. The server then performs the requested operation. The NFS client automatically converts all mounted directories and file structures, contents, and names to the format required by OpenVMS. For example, a UNIX file named /usr/webster/.login would appear to an OpenVMS client as DNFS1:[USR.WEBSTER].LOGIN;1

For more information on how NFS converts file names, see Appendix C.

21.1.2 Storing File Attributes

The OpenVMS operating system supports multiple file types and record formats. In contrast, NFS and UNIX systems support only byte-stream files, seen to the OpenVMS client as sequential STREAM_LF files.

This means the client must use special record handling to store and access non-STREAM_LF files. The OpenVMS NFS client accomplishes this with attribute description files (ADFs). These are special companion files the client uses to hold the attribute information that would otherwise be lost in the translation to STREAM_LF format. For example, a SET FILE/NOBACKUP command causes the client to create an ADF, because NFS has no concept of this OpenVMS attribute. Using Default ADFs

The client provides default ADFs for files with the following extensions: .EXE, .HLB, .MLB, .OBJ, .OLB, .STB, and .TLB. (The client does not provide ADFs for files with the .TXT and .C extensions, because these are STREAM_LF.) The client maintains these ADFs on the server.

For example, SYS$SYSTEM:TCPIP$EXE.ADF is the default ADF for all .EXE type files. When you create .EXE files (or if they exist on the server), they are defined with the record attributes from the single default ADF file. The client refers only to the record attributes and file characteristics fields in the default ADF. How the Client Uses ADFs

By default, the client uses ADFs if they exist on the server. The client updates existing ADFs or creates them as needed for new files. If you create a non-STREAM_LF OpenVMS file or a file with access control lists (ACLs) associated with it on the NFS server, the NFS client checks to see whether a default ADF can be applied. If not, the client creates a companion ADF to hold the attributes.

The client hides these companion files from the user's view. If a user renames or deletes the orginal file, the client automatically renames or deletes the companion file. However, if a user renames or deletes a file on the server side, the user must also rename the companion file; otherwise, file attributes are lost.

You can modify this behavior with the /NOADF qualifier to the MOUNT command. The /NOADF qualifier tells the client to handle all files as STREAM_LF unless a default ADF matches. This mode is only appropriate for read-only file systems because the client cannot adequately handle application-created files when /NOADF is operational. Creating Customized Default ADFs

You can create customized default ADFs for special applications. To do so:

  1. On the client, create a special application file that results in creating an ADF on the server. Suppose that application file is called TEST.GAF .
  2. On the server, check the listing for the newly created file. For example:

    > ls -a

    Note that the ADF ( .$ADF$test.gaf;1 ) was created with the data file ( TEST.GAF ).
  3. On the server, copy the ADF file to a newly created default ADF file on the client. For example:

    > cp .\$ADF\$test.gaf\;1 gaf.adf

    Note that the backslashes (\) are required for entering the UNIX system nonstandard dollar sign ($) and semicolon (;) symbols.
  4. On the client, copy the new default ADF file to the SYS$SYSTEM directory. For example:

  5. Dismount all the NFS volumes and mount them again. This starts another NFS ancillary control process (ACP) so that the newly copied default ADF file can take effect.

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