Technical data

NFS Server
20.13 Modifying File System Characteristics
Table 20–4 (Cont.) File System Logical Names
Logical Name Description
TCPIP$CFS_FATAL_MESSAGES Defines the terminal device to which the important error
messages are directed, in addition to the normal error messages
that are sent to the operator’s console.
The default is _OPA0:.
20.14 File Locking
TCP/IP Services supports a partial implementation of NFS network locking,
which allows users to lock files. The software coordinates locks among remote
users and between remote and local users. The file locking features is applicable
regardless of whether the OpenVMS Record Management Services (RMS) is used.
However, NFS does not coordinate network locking and RMS record locks.
Note
This version of NFS does not support byte-range locking. If a byte-range
lock request is received, it is handled as a file lock request.
File locking is implemented using the Network Lock Manager (NLM) (also known
remote procedure call, or RPC, lockd ) and the Network Status Monitor (NSM)
(also known as RPC statd ). The NLM coordinates locks made by clients. The
NSM recovers lock information in case the server or client fails. The NSM uses
the NLM to keep the host list when the client or the server fails and reboots, as
follows:
• If the client fails and reboots, it notifies the NSMs on its host list. In turn,
the NSMs tell their local NLMs to free any locks held for that client.
• If the server fails, when it reboots it notifies the NSMs on each client host in
its host list. In turn, the client NSMs tell their local NLMs to request again
all the locks that were granted on their behalf by the server before it failed.
The NSM and the NLM are enabled if you select LOCKD/STATD in the
TCPIP$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:
SYS$STARTUP:TCPIP$LOCKD_SYSTARTUP.COM
NFS Server 20–19