HP OpenVMS Systems Documentation

If you are using DECnet--Plus, a separate step is not required to start the network. DECnet--Plus starts automatically on the next reboot after the node has been configured using the NET$CONFIGURE.COM procedure.

If you are using DECnet for OpenVMS, at the system prompt, enter the following command to start the network:

$ @SYS$MANAGER:STARTNET.COM

To ensure that the network is started each time an OpenVMS Cluster computer boots, add that command line to the appropriate startup command file or files. (Startup command files are discussed in Section 5.6.)

4.5.8 What is the Cluster Alias?

The cluster alias acts as a single network node identifier for an OpenVMS Cluster system. When enabled, the cluster alias makes all the OpenVMS Cluster nodes appear to be one node from the point of view of the rest of the network.

Computers in the cluster can use the alias for communications with other computers in a DECnet network. For example, networked applications that use the services of an OpenVMS Cluster should use an alias name. Doing so ensures that the remote access will be successful when at least one OpenVMS Cluster member is available to process the client program's requests.

Rules:

• DECnet for OpenVMS (Phase IV) allows a maximum of 64 OpenVMS Cluster computers to participate in a cluster alias. If your cluster includes more than 64 computers, you must determine which 64 should participate in the alias and then define the alias on those computers.
  At least one of the OpenVMS Cluster nodes that uses the alias node identifier must have level 1 routing enabled.
  • On Alpha nodes, routing between multiple circuits is not supported. However, routing is supported to allow cluster alias operations. Level 1 routing is supported only for enabling the use of a cluster alias. The DVNETEXT PAK must be used to enable this limited function.
  • On VAX nodes, full level 1 routing support is available.
  • On both Alpha and VAX systems, all cluster nodes sharing the same alias node address must be in the same area.
• DECnet--Plus allows a maximum of 96 OpenVMS Cluster computers to participate in the cluster alias.
  DECnet--Plus does not require that a cluster member be a routing node, but an adjacent Phase V router is required to use a cluster alias for DECnet--Plus systems.
• A single cluster alias can include nodes running either DECnet for OpenVMS or DECnet--Plus, but not both.

If you have defined a cluster alias and have enabled routing as shown in Section 4.5.6, you can enable alias operations for other computers after the computers are up and running in the cluster. To enable such operations (that is, to allow a computer to accept incoming connect requests directed toward the alias), follow these steps:

1. Log in as system manager and invoke the SYSMAN utility. For example:

   $ RUN SYS$SYSTEM:SYSMAN SYSMAN>

2. At the SYSMAN> prompt, enter the following commands:

   SYSMAN> SET ENVIRONMENT/CLUSTER %SYSMAN-I-ENV, current command environment: Clusterwide on local cluster Username SYSTEM will be used on nonlocal nodes SYSMAN> SET PROFILE/PRIVILEGES=(OPER,SYSPRV) SYSMAN> DO MCR NCP SET EXECUTOR STATE OFF %SYSMAN-I-OUTPUT, command execution on node X... . . . SYSMAN> DO MCR NCP DEFINE EXECUTOR ALIAS INCOMING ENABLED %SYSMAN-I-OUTPUT, command execution on node X... . . . SYSMAN> DO @SYS$MANAGER:STARTNET.COM %SYSMAN-I-OUTPUT, command execution on node X... . . .

Note: Compaq does not recommend enabling alias operations for satellite nodes.

Reference: For more details about DECnet for OpenVMS networking and cluster alias, see the DECnet for OpenVMS Networking Manual and DECnet for OpenVMS Network Management Utilities. For equivalent information about DECnet--Plus, see the DECnet--Plus documentation.

In any OpenVMS Cluster environment, it is best to share resources as much as possible. Resource sharing facilitates workload balancing because work can be distributed across the cluster.

5.1 Shareable Resources

Most, but not all, resources can be shared across nodes in an OpenVMS Cluster. The following table describes resources that can be shared.

5.1.1 Local Resources

Figure 5-1 shows an example of an OpenVMS Cluster system that has both an Alpha system disk and a VAX system disk, and a dual-ported disk that is set up so the environmental files can be shared between the Alpha and VAX systems.

Figure 5-1 Resource Sharing in Mixed-Architecture Cluster System

Depending on your processing needs, you can prepare either an environment in which all environmental files are shared clusterwide or an environment in which some files are shared clusterwide while others are accessible only by certain computers.

The following table describes the characteristics of common- and multiple-environment clusters.

The installation or upgrade procedure for your operating system generates a common system disk, on which most operating system and optional product files are stored in a common root directory.

5.3.1 Directory Roots

The system disk directory structure is the same on both Alpha and VAX systems. Whether the system disk is for Alpha or VAX, the entire directory structure---that is, the common root plus each computer's local root---is stored on the same disk. After the installation or upgrade completes, you use the CLUSTER_CONFIG.COM command procedure described in Chapter 8 to create a local root for each new computer to use when booting into the cluster.

In addition to the usual system directories, each local root contains a [SYSn.SYSCOMMON] directory that is a directory alias for [VMS$COMMON], the cluster common root directory in which cluster common files actually reside. When you add a computer to the cluster, CLUSTER_CONFIG.COM defines the common root directory alias.

5.3.2 Directory Structure Example

Figure 5-2 illustrates the directory structure set up for computers JUPITR and SATURN, which are run from a common system disk. The disk's master file directory (MFD) contains the local roots (SYS0 for JUPITR, SYS1 for SATURN) and the cluster common root directory, [VMS$COMMON].

Figure 5-2 Directory Structure on a Common System Disk

The logical name SYS$SYSROOT is defined as a search list that points first to a local root (SYS$SYSDEVICE:[SYS0.SYSEXE]) and then to the common root (SYS$COMMON:[SYSEXE]). Thus, the logical names for the system directories (SYS$SYSTEM, SYS$LIBRARY, SYS$MANAGER, and so forth) point to two directories.

Figure 5-3 shows how directories on a common system disk are searched when the logical name SYS$SYSTEM is used in file specifications.

Figure 5-3 File Search Order on Common System Disk

Important: Keep this search order in mind when you manipulate system files on a common system disk. Computer-specific files must always reside and be updated in the appropriate computer's system subdirectory.

Examples

1. MODPARAMS.DAT must reside in SYS$SPECIFIC:[SYSEXE], which is [SYS0.SYSEXE] on JUPITR, and in [SYS1.SYSEXE] on SATURN. Thus, to create a new MODPARAMS.DAT file for JUPITR when logged in on JUPITR, enter the following command:

   $ EDIT SYS$SPECIFIC:[SYSEXE]MODPARAMS.DAT

   
   Once the file is created, you can use the following command to modify it when logged on to JUPITR:

   $ EDIT SYS$SYSTEM:MODPARAMS.DAT

   
   Note that if a MODPARAMS.DAT file does not exist in JUPITR's SYS$SPECIFIC:[SYSEXE] directory when you enter this command, but there is a MODPARAMS.DAT file in the directory SYS$COMMON:[SYSEXE], the command edits the MODPARAMS.DAT file in the common directory. If there is no MODPARAMS.DAT file in either directory, the command creates the file in JUPITR's SYS$SPECIFIC:[SYSEXE] directory.
2. To modify JUPITR's MODPARAMS.DAT when logged in on any other computer that boots from the same common system disk, enter the following command:

   $ EDIT SYS$SYSDEVICE:[SYS0.SYSEXE]MODPARAMS.DAT

3. To modify records in the cluster common system authorization file in a cluster with a single, cluster-common system disk, enter the following commands on any computer:

   $ SET DEFAULT SYS$COMMON:[SYSEXE] $ RUN SYS$SYSTEM:AUTHORIZE

4. To modify records in a computer-specific system authorization file when logged in to another computer that boots from the same cluster common system disk, you must set your default directory to the specific computer. For example, if you have set up a computer-specific system authorization file (SYSUAF.DAT) for computer JUPITR, you must set your default directory to JUPITR's computer-specific [SYSEXE] directory before invoking AUTHORIZE, as follows:

   $ SET DEFAULT SYS$SYSDEVICE:[SYS0.SYSEXE] $ RUN SYS$SYSTEM:AUTHORIZE

Clusterwide logical names were introduced in OpenVMS Version 7.2 for both OpenVMS Alpha and OpenVMS VAX. Clusterwide logical names extend the convenience and ease-of-use features of shareable logical names to OpenVMS Cluster systems.

Existing applications can take advantage of clusterwide logical names without any changes to the application code. Only a minor modification to the logical name tables referenced by the application (directly or indirectly) is required.

New logical names are local by default. Clusterwide is an attribute of a logical name table. In order for a new logical name to be clusterwide, it must be created in a clusterwide logical name table.

Some of the most important features of clusterwide logical names are:

• When a new node joins the cluster, it automatically receives the current set of clusterwide logical names.
• When a clusterwide logical name or name table is created, modified, or deleted, the change is automatically propagated to every other node in the cluster running OpenVMS Version 7.2 or later. Modifications include security profile changes to a clusterwide table.
• Translations are done locally so there is minimal performance degradation for clusterwide name translations.
• Because LNM$CLUSTER_TABLE and LNM$SYSCLUSTER_TABLE exist on all systems running OpenVMS Version 7.2 or later, the programs and command procedures that use clusterwide logical names can be developed, tested, and run on nonclustered systems.

To support clusterwide logical names, the operating system creates two clusterwide logical name tables and their logical names at system startup, as shown in Table 5-1. These logical name tables and logical names are in addition to the ones supplied for the process, job, group, and system logical name tables. The names of the clusterwide logical name tables are contained in the system logical name directory, LNM$SYSTEM_DIRECTORY.

The definition of LNM$SYSTEM has been expanded to include LNM$SYSCLUSTER. When a system logical name is translated, the search order is LNM$SYSTEM_TABLE, LNM$SYSCLUSTER_TABLE. Because the definitions for the system default table names, LNM$FILE_DEV and LNM$DCL_LOGICALS, include LNM$SYSTEM, translations using those default tables include definitions in LNM$SYSCLUSTER.

The current precedence order for resolving logical names is preserved. Clusterwide logical names that are translated against LNM$FILE_DEV are resolved last, after system logical names. The precedence order, from first to last, is process --> job --> group --> system --> cluster, as shown in Figure 5-4.

Figure 5-4 Translation Order Specified by LNM$FILE_DEV

You might want to create additional clusterwide logical name tables for the following purposes:

• For a multiprocess clusterwide application to use
• For members of a UIC group to share

To create a clusterwide logical name table, you must have create (C) access to the parent table and write (W) access to LNM$SYSTEM_DIRECTORY, or the SYSPRV (system) privilege.

A shareable logical name table has UIC-based protection. Each class of user (system (S), owner (O), group (G), and world (W)) can be granted four types of access: read (R), write (W), create (C), or delete (D).

You can create additional clusterwide logical name tables in the same way that you can create additional process, job, and group logical name tables---with the CREATE/NAME_TABLE command or with the $CRELNT system service. When creating a clusterwide logical name table, you must specify the /PARENT_TABLE qualifier and provide a value for the qualifier that is a clusterwide table name. Any existing clusterwide table used as the parent table will make the new table clusterwide.

The following example shows how to create a clusterwide logical name table:

$ CREATE/NAME_TABLE/PARENT_TABLE=LNM$CLUSTER_TABLE -
_$ new-clusterwide-logical-name-table

Alias collisions involving clusterwide logical name tables are treated differently from alias collisions of other types of logical name tables. Table 5-2 describes the types of collisions and their outcomes.