MOUNT Command Qualifiers for Shadowing
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This section briefly describes the MOUNT command qualifiers that are useful for shadow set management. See also the HP OpenVMS System Management Utilities Reference Manual for complete information about these and other DCL commands.
You must use the /SHADOW qualifier when you create a new shadow set or when you add a member to an existing shadow set. You can also use the optional qualifiers described in Table 4-1 and in Table 4-2. These qualifiers require the VOLPRO and OPER privileges, or your user identification code (UIC) must match the owner UIC of the volume being mounted. To mount a shadow set throughout the system, you must also have the SYSNAM privilege. In addition, the MOUNT/POLICY=[NO]MINICOPY[=OPTIONAL] command requires the LOG_IO privilege.
Detailed examples and descriptions of how to use these qualifiers are included in “Adding Shadow Set Members ”. In addition to the shadowing-specific qualifiers described in Table 4-1, the /NOASSIST, /SYSTEM, /GROUP, and /CLUSTER qualifiers are also frequently used when mounting shadow sets, as described in Table 4-2 and in “Additional MOUNT Command Qualifiers Used for Shadowing”.
Table 4-1 describes the MOUNT command qualifiers that are specific to shadowing.
Table 4-1 MOUNT Command Qualifiers (Shadowing Specific)
| Qualifier | Function |
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/[NO]CONFIRM | Controls whether the Mount utility issues a request to confirm a copy operation when mounting a shadow set. The default is /NOCONFIRM. |
/[NO]COPY | Enables or disables copy operations on physical devices named when mounting or adding to a shadow set. The default is /COPY. |
/[NO]INCLUDE | Automatically mounts and reinstates a shadow set to the way it was before the shadow set was dissolved. The default is /NOINCLUDE. |
/OVERRIDE= NO_FORCED_ ERROR | Directs the Mount utility to proceed with shadowing, even though the device or controller does not support forced error handling. Using unsupported SCSI disks can cause members to be removed from a shadow set if certain error conditions arise that cannot be corrected, because some SCSI disks do not implement READL and WRITEL commands that support disk bad-block repair. If the SCSI device does not support READL and WRITEL commands, the SCSI disk class driver sets a NOFE (no forced error) bit in a System Dump Analyzer display. See “Using SDA to Obtain Information About Third-Party SCSI Devices” for more information. |
/OVERRIDE= SHADOW_ MEMBERSHIP | Mounts a former shadow set member and zeroes the disk's shadow set generation number so that the disk is no longer marked as having been a member of the shadow set. |
Controls the setup and use of the shadowing minicopy function. This qualifier requires LOG_IO privilege. The meaning of [NO]MINICOPY[=OPTIONAL] depends on the status of the shadow set. If the shadow set is not mounted, either on a standalone system or on any cluster member, and MINICOPY=OPTIONAL is specified, the shadow set is mounted and a write bitmap is created. (A write bitmap enables a shadowing minicopy operation.) MOUNT/POLICY=MINICOPY[=OPTIONAL] must be specified on the initial mount of a shadow set, either on a standalone system or in a cluster, to enable the shadowing minicopy operation. The OPTIONAL keyword allows the mount to continue, even if the system was unable to start the write bitmap. A bitmap could fail to start properly because of an improperly dismounted shadow set, a shadow set that requires a merge operation, or various resource problems. If the OPTIONAL keyword is omitted and the system is unable to start the write bitmap, the shadow set is not mounted. If you specify /POLICY=MINICOPY=OPTIONAL and the shadow set was already mounted on another node in the cluster without this qualifier and keyword, the MOUNT command succeeds but a write bitmap is not created. If NOMINICOPY is specified, the shadow set is mounted but a write bitmap is not created. If a former member of the the shadow set is returned to the shadow set, which has minicopy enabled, then a minicopy is started instead of a full copy. This is the default behavior and occurs even if you omit /POLICY=MINICOPY[=OPTIONAL]. If a minicopy successfully starts and then fails for some reason, a full copy is performed. If a minicopy cannot be started and the keyword OPTIONAL was omitted, the mount fails. If NOMINICOPY is specified, then a minicopy is not performed, even if one is possible. | |
/POLICY= REQUIRE_ MEMBERS | Controls whether every physical device specified with the /SHADOW qualifier must be accessible when the MOUNT command is issued in order for the MOUNT command to take effect. The proposed members are either specified in the command line or found on the disk by means of the /INCLUDE qualifier. The behavior, without this qualifier, is that if one or more members is not accessible for any reason (such as a connectivity failure), then the virtual unit is created with the members that are accessible. This option is especially useful in the recovery of disaster-tolerant clusters because it ensures that the correct membership is selected after an event. |
/POLICY= VERIFY_LABEL | Requires that any member to be added to the shadow set have a volume label of SCRATCH_DISK. This helps ensure that the wrong disk is not added to a shadow set by mistake. If you plan to use VERIFY_LABEL, then before using this qualifier you must either initialize the disk to be added to the set with the label SCRATCH_DISK, or specify a label for the disk with the command SET VOLUME/LABEL. The default behavior is NOVERIFY_LABEL, which means that the volume label of the copy targets is not checked. This is the same behavior that occurred before the introduction of this qualifier. The volume label of the copy targets is not checked. |
/SHADOW= (physical-device-name[:][,...]) | Directs the Mount utility to bind the specified physical devices into a shadow set represented by the virtual unit named in the command. |
The MOUNT command qualifiers described in this section are not specific to shadowing but can be very useful when creating shadow sets. These additional qualifiers are described in Table 4-2 and in the examples that follow.
Table 4-2 Additional MOUNT Command Qualifiers (Not Shadowing Specific)
You may occasionally find it useful to specify the /NOASSIST qualifier on the MOUNT command. For example, you can use the MOUNT/NOASSIST command in startup files to avoid failure of a MOUNT command when a device you specify in the command is not available. The /NOASSIST qualifier can be used in startup files because operator intervention is impossible during startup.
The MOUNT/NOASSIST qualifier can successfully mount the shadow set as long as at least one of the devices included in the MOUNT command is available for mounting. Example 4-2 shows an example of the /NOASSIST qualifier and the resulting messages when one of the members included in the command is not available for mounting.
Example 4-2 Using the /NOASSIST Qualifier
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$MOUNT/SYS DSA65:/SHADOW=($4$DIA6,$4$DIA5) GALEXY/NOASSIST %MOUNT-I-MOUNTED, GALEXY mounted on _DSA65: %MOUNT-I-SHDWMEMSUCC, _$4$DIA6: (READY) is now a valid member of the shadowset %MOUNT-I-SHDWMEMFAIL, $4$DIA5 failed as a member of the shadow set -SYSTEM-F-VOLINV, volume is not software enabled |
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Even though device $4$DIA5 is not available for mounting, the MOUNT command continues to create the shadow set with $4$DIA6 as its only member. If the command did not include the /NOASSIST qualifier, the MOUNT command would not mount the shadow set.
When you create a shadow set, you must specify either the /SYSTEM qualifier or the /CLUSTER qualifier, or both (see Table 4-2) to provide access for all users on a single system or on a cluster.
In Example 4-3, if the shadow set (identified by its virtual unit name DSA2) is not currently mounted, the first command creates a shadow set with one shadow set member; the second command adds two more members to the same shadow set. An automatic copy operation causes any data on the second and third volumes to be overwritten as the shadow set members are added.
In the second MOUNT command, you have to specify only the /SYSTEM when you add the $6$DIA5 and $6$DIA6 devices to the shadow set. Do not use /CLUSTER. These disks are added with the same status that the shadow set currently has, which in this case is clusterwide access.