OpenVMS System Manager's Manual

When a device goes off line or is write-locked, mount verification sends two messages:

• One message goes to OPCOM.
• The other message, distinguished by the prefix %SYSTEM-I-MOUNTVER, goes directly to the system console (OPA0:), bypassing OPCOM.

The second message is a form of insurance in cases in which OPCOM is unavailable. For example, if the system disk undergoes mount verification or if OPCOM is not present on a system, you at least receive the messages with the %SYSTEM-I-MOUNTVER prefix. Under normal circumstances, the operator terminal receives both messages, with the %SYSTEM-I-MOUNTVER message arriving first.

These messages notify you of the problem, and allow you to correct the problem and recover the operation. When a pending mount verification is canceled by timing out, OPCOM prints a message in the following format:

%%%%%%%%%%% OPCOM, <dd-mmm-yyyy hh:mm:ss.cc> %%%%%%%%%%% 
Mount verification aborted for device <device-name>. 

After a mount verification times out, all pending and future I/O requests to the volume fail. You must dismount and remount the disk before users can access it again.

Note

Mount verification caused by a write-lock error does not time out.

Mount Verification and Write-Locking

Suppose, for example, that a volume is mounted on a drive with write-lock off, and someone toggles the WRITE LOCK switch. If mount verification is enabled for the volume, the volume enters mount verification, and all I/O operations to the volume are suspended until you recover the operation, as explained in Section 8.13.2.4.

At mount time, if the system detects that the caches were not written back the last time the volume was used, the system automatically rebuilds the file information by scanning the contents of the volume. However, files being written at the time of the improper dismount might be partially or entirely lost. See Section 8.12 for details about analyzing and repairing these problems.

With the mount verification feature of disk and tape handling, users are generally unaware that a mounted disk or tape has gone off line and returned on line, or in some other way has become unreachable and then restored.

8.13.2 Using Mount Verification

The following sections explain how to perform these tasks:

Task	Section
Enable and disable mount verification	Section 8.13.2.1
Control timeout periods for mount verification	Section 8.13.2.2
Recover from offline errors	Section 8.13.2.3
Recover from write-lock errors	Section 8.13.2.4
Cancel mount verification	Section 8.13.2.5

8.13.2.1 Enabling Mount Verification

Mount verification is enabled by default when you mount a disk or tape. To disable mount verification, you must specify /NOMOUNT_VERIFICATION when you mount a disk or tape.

Note that this feature applies to standard mounted tapes, foreign mounted tapes, and Files-11 disks.

8.13.2.2 Controlling Timeout Periods for Mount Verification

You can control the amount of time (in seconds) that is allowed for a mount verification to complete before it is automatically canceled. The MVTIMEOUT system parameter for disks and the TAPE_MVTIMEOUT system parameter for tapes define the time (in seconds) that is allowed for a pending mount verification to complete before it is automatically canceled. (See the OpenVMS System Management Utilities Reference Manual for more information on system parameters.)

Always set either parameter to a reasonable value for the typical operations at your site. Note that resetting the value of the parameter does not affect a mount verification that is currently in progress. Ten minutes (600 seconds) is usually a good value for MVTIMEOUT and TAPE_MVTIMEOUT, whether or not an operator is usually present.

8.13.2.3 Recovering from Offline Errors

When a mounted disk or tape volume goes off line while mount verification is enabled, you can try to recover, or you can terminate the mount request. The following options are available:

• Try to put the device back on line by toggling the START or RUN button on disks or the LOAD button on tapes. If the device has failed, terminate mount verification.
• Take the disk or tape out of the offline and verification-pending state by shutting down mount verification with one of the three techniques described in Section 8.13.2.5. These techniques include canceling the mount request, dismounting the volume, and allowing mount verification to time out.

If you successfully put the device back on line, the mount verification software that polls the disk or tape drive begins verification in the following sequence of steps:

1. The system checks to see that the currently mounted disk or tape has the same identification as the previously mounted volume. In this way, mount verification confirms that this is the same disk or tape that was previously mounted and no switching has occurred.
   If the drive contains the wrong volume, OPCOM issues a message in this format:

   %%%%%%%%%%% OPCOM, <dd-mmm-yyyy hh:mm:ss.cc> %%%%%%%%%%% 
   Device <device-name> contains the wrong volume. 
   Mount verification in progress. 
   

2. Once mount verification completes, the disk is marked as valid, and OPCOM issues a message in the following format:

   %%%%%%%%%%% OPCOM, <dd-mmm-yyyy hh:mm:ss.cc> %%%%%%%%%%% 
   Mount verification completed for device <device-name>. 
   

3. I/O operations to the disk or tape proceed, as shown in the following example:

   %%%%%%%%%%% OPCOM, 28-MAY-1996 11:54:54.12 %%%%%%%%%%% 
   Device DUA0: is offline. 
   Mount verification in progress. 
    
   %%%%%%%%%%% OPCOM, 28-MAY-1996 11:57:34.22 %%%%%%%%%%% 
   Mount verification completed for device DUA0:. 
   

   
   In this example, the message from OPCOM informs the operator that device DUA0: went off line and mount verification was initiated. The operator finds that the drive was accidentally powered down and successfully powers it up again.
   The last message in the example indicates that mount verification is satisfied that the same volume is on the drive as before the error. All I/O operations to the volume resume.

Devices become write-locked when a hardware or user error occurs while a disk or a tape volume is mounted for a write operation. For example, if a disk is write-locked or a tape is missing a write ring, the hardware generates an error. As soon as the software discovers that the disk or tape is write-locked (for example, when an I/O operation fails with a write-lock error), mount verification begins.

OPCOM issues a message in the following format to the operators enabled for DISKS and DEVICES or TAPES and DEVICES, announcing the unavailability of the disk or tape:

%%%%%%%%%%%% OPCOM, <dd-mmm-yyyy hh:mm:ss.cc> %%%%%%%%%%% 
Device <device-name> has been write-locked. 
Mount verification in progress. 

You can either recover the operation or terminate mount verification. Your options include the following:

• Enable the drive for writing by toggling the hardware WRITE LOCK switch of the disk, or check to see that a tape volume has a write ring.
• If the disk or tape drive is faulty, but another functioning drive is available on the same controller, move the disk or tape to the functioning drive and swap the unit select plugs. (Note that switching to another drive causes the volume to undergo offline mount verification; once this completes, the write-lock mount verification continues.)
• Terminate the mount operation by shutting down mount verification with one of the techniques described in Section 8.13.2.5.

Once the mount verification software determines that the volume is in a write-enabled state, I/O operations to the tape or disk resume with no further messages.

8.13.2.5 Canceling Mount Verification

You can cancel a mount verification request in one of the following ways:

• Dismount the volume with the DCL command DISMOUNT from a process that is not hung.
• If the device is off line, allow mount verification to time out. The expiration value is 10 minutes by default; however, you can use the system parameter MVTIMEOUT (for disk) or TAPE_MVTIMEOUT (for tape) to set the value to whatever you want. When the time expires, the system automatically cancels the pending mount verification. Note that a mount verification initiated by a write-lock condition does not time out.
• Invoke a special canceling routine from the console terminal.

The following sections describe these methods in more detail.

Using the DISMOUNT Command

To dismount a volume, follow these steps:

1. Log in at another terminal, or use any logged-in terminal that has access to the volume. (It does not need to be an operator terminal.)
2. Enter the DISMOUNT/ABORT command for the volume. (To use the /ABORT qualifier with a volume that is not mounted group or system, you must have volume ownership or the user privilege VOLPRO.)
   If your system is in an OpenVMS Cluster environment, also specify the /CLUSTER qualifier.
   When you cancel a pending mount verification by dismounting the volume, OPCOM issues a message in the following format:

   %%%%%%%%%%%% OPCOM, <dd-mmm-yyyy hh:mm:ss.cc> %%%%%%%%%%% 
   Mount verification aborted for device <device-name>. 
   

   
   If you do not have access to the volume, you receive an error message. You can try again if you can find an appropriate process to use. If your process hangs, the system file ACP is hung, and you cannot use this technique to cancel mount verification.
3. When the cancellation is complete, remove the volume from the drive.

Using Cancellation Commands

To cancel mount verification, you run a special interrupt program called Interrupt Priority C (IPC). IPC issues a software interrupt to gain the attention of the operating system. You use IPC to cancel mount verification, enter the debugger, or recalculate the quorum on an OpenVMS Cluster system. (The debugger in this case refers to the system-level debugger, XDELTA.)

The IPC program converts lowercase characters to uppercase, issues the terminal bell character whenever it receives illegal characters (such as most control characters), compresses multiple spaces, and ignores leading spaces.

How to Perform This Task

1. Invoke IPC by using commands specific to the hardware you are using. Display the console prompt and enter a sequence of commands from the console terminal.
   On VAX systems, enter the following commands:

   >>> HALT
   >>> D/I 14 C
   >>> CONT
   IPC> 
   

   
   On Alpha systems, enter the following commands:

   >>> HALT
   >>> D SIRR C
   >>> CONT
   IPC> 
   

2. Enter one of the following commands in response to the IPC> prompt:

   Command	Explanation
   C device-name	Cancels any pending mount verification on the device specified. (A warning is given if no mount verification was in progress for that device.) For example: IPC> C MUA1:
   X	Transfers control to the debugging tool XDELTA (provided it was loaded with the system by setting the appropriate value in the boot file). If XDELTA has not been loaded, the prompt IPC> is reissued. For example: IPC> X
   Q	Recalculates the quorum in an OpenVMS Cluster system.

   
   When a pending mount verification is canceled, OPCOM prints a message in the following format:

   %%%%%%%%%%% OPCOM, <dd-mmm-yyyy hh:mm:ss.cc> %%%%%%%%%%% 
   Mount verification aborted for device <device-name>. 
   

3. Exit from IPC by pressing Ctrl/Z.
4. After you successfully cancel a pending mount verification with this technique, you must dismount and then remount the volume before you can access it again.

Example

%%%%%%%%%%% OPCOM, 28-MAY-1996 10:54:54.12 %%%%%%%%%%% 
        Device DUA0: is offline. 
        Mount verification in progress. 

On VAX systems, you might enter the following commands:

>>> HALT
>>> D/I 14 C
>>> CONT
IPC> C DUA0:
IPC> [Ctrl/Z]
%SYSTEM-I-MOUNTVER, _DUA0: has aborted mount verification.
%%%%%%%%%%% OPCOM, 28-MAY-1996 10:56:26.13 %%%%%%%%%%%
Mount verification aborted for device DUA0: 

On Alpha systems, you might enter the following commands:

>>> HALT
>>> D SIRR C
>>> CONT
IPC> C DUA0:
IPC> [Ctrl/Z]
%SYSTEM-I-MOUNTVER, _DUA0: has aborted mount verification.
%%%%%%%%%%% OPCOM, 28-MAY-1996 10:56:26.13 %%%%%%%%%%%
Mount verification aborted for device DUA0: 

In both examples, device DUA0: is off line, but you are unable to spin the disk back up. No other drive is available on the controller, so you cannot switch the unit select plugs of the two drives.

Do not enter a DISMOUNT command for the disk, because it was mounted as a private volume, and you do not have access to it. The %SYSTEM-I-MOUNTVER message also appears because this is the console terminal.

8.14 Using the Bad Block Locator Utility to Detect Media Errors

The DCL command ANALYZE/MEDIA invokes the optional Bad Block Locator utility (BAD), which analyzes block-addressable media and records the location of blocks that cannot reliably store data.

Note

Many newer devices automatically check for bad blocks; therefore, BAD is more useful with older devices that do not check for bad blocks.

To test the blocks on a volume, ANALYZE/MEDIA does the following:

• Writes a test pattern to each block on the media
• Reads the contents of the block into a buffer
• Compares the data read back with the data written

If the data does not compare exactly, a block cannot reliably store data.

When the Bad Block Locator utility locates a bad block, it records the address of the block. Consecutive bad blocks are recorded as single entries for non-last-track devices. After it finishes testing the disk, BAD writes the addresses of the bad blocks into a file called the detected bad block file (DBBF).

Caution

Testing a volume for bad blocks destroys its contents. However, you can update the detected bad block file (DBBF) without erasing the contents of the volume by using the ANALYZE/MEDIA qualifiers /NOEXERCISE and /BAD_BLOCKS.

How to Perform This Task

To use BAD, perform the following steps:

1. Allocate the device with the DCL command ALLOCATE (to ensure that the device is not accessed by any other programs).
2. Enter the DCL command MOUNT/FOREIGN.
   When the device is mounted as foreign, the system does not recognize it as a Files--11 volume, and BAD can execute.
3. Enter the DCL command ANALYZE/MEDIA.

Refer to online help or to the archived manual OpenVMS Bad Block Locator Utility Manual for details on using the Bad Block Locator utility.

This chapter discusses concepts and tasks related to file protection, file manipulation, and data transfer.

Information Provided in This Chapter

This chapter describes the following tasks:

Task	Section
Getting file information	Section 9.2
Protecting disk files	Section 9.3.3
Protecting disk directories	Section 9.3.4
Protecting magnetic tape files	Section 9.3.5
Accessing disk files	Section 9.4
Accessing tape files	Section 9.5
Copying and transferring files	Section 9.6

This chapter explains the following concepts:

Concept	Section
DCL commands with files	Section 9.1
File protection	Section 9.3.1
Tape file names	Section 9.5.1

9.1 Using DCL Commands with Files

You use the DIGITAL Command Language (DCL) to perform a number of operations on files; among them are the following:

Operation	DCL Command
Retrieve disk and magnetic tape file information, such as device and protection characteristics, and display this information on your terminal screen	SHOW commands listed in Table 9-1
Modify disk file characteristics, such as protection or UIC information	SET commands listed in Table 9-3
Display the contents of a directory	DIRECTORY
Display the contents of a file	TYPE
Copy files to and from disk and magnetic tape volumes	COPY

Most DCL commands require file-structured devices. (The OpenVMS DCL Dictionary lists commands that do not require file-structured devices.)

In addition to manipulating files through DCL, you can write programs to assist you in routine file-manipulation tasks. You can write these programs in any of the languages supported by the operating system.

To manipulate individual records within files (that is, to access files at the record level), write programs that include OpenVMS Record Management Services (RMS) facilities. Examples of the RMS facilities used to manipulate files at the record level are in the OpenVMS Record Management Services Reference Manual.

9.2 Getting File Information

Use the DCL command DIRECTORY to retrieve information about disk and magnetic tape files in a directory, using the following format:

DIRECTORY [filespec[,...]] 

When you include certain command qualifiers with the DIRECTORY command, you can retrieve information in addition to a list of the names of the files in the directory. See the OpenVMS DCL Dictionary for a list of qualifiers that you can use with the DIRECTORY command.

The following examples illustrate three cases of retrieving information from the [MALCOLM] directory, which resides on a disk with the logical name DISK$DOCUMENT.

Examples

1. $ DIRECTORY AVERAGE.*
    
   Directory DISK$DOCUMENT:[MALCOLM]
    
   AVERAGE.EXE;6      AVERAGE.FOR;6      AVERAGE.LIS;4     AVERAGE.OBJ;12
    
   Total of 4 files.  
   

   
   The DIRECTORY command in this example lists all file types of the AVERAGE file and the version number of each file. The command would also list all versions of these files; however, only one version of each file exists.

2. $ DIRECTORY/SIZE/DATE/VERSIONS=1/PROTECTION  AVERAGE
    
   Directory DISK$DOCUMENT:[MALCOLM] 
    
   AVERAGE.EXE;6       6        10-APR-1996 15:43 (RWED,RWED,RWED,RE)
   AVERAGE.FOR;6       2         2-APR-1996 10:29 (RWED,RWED,RWED,RE)
   AVERAGE.LIS;4       5         9-APR-1996 16:27 (RWED,RWED,RWED,RE)
   AVERAGE.OBJ;6       2         9-APR-1996 16:27 (RWED,RWED,RWED,RE)
    
   Total of 4 files, 15 blocks.
   

   
   The DIRECTORY command in this example displays all the file types of the AVERAGE file and the version number of each file. The /SIZE qualifier displays the size of each file in blocks used. The /DATE qualifier displays the creation date of the version of the file that is listed. The VERSIONS=1 qualifier limits the number of versions of the file displayed to one (the most recent) version. The /PROTECTION qualifier displays the file protection for each file.

3. $ DIRECTORY/FULL/VERSIONS=1 [MALCOLM...]AVERAGE.EXE
     
   Directory DISK$DOCUMENT:[MALCOLM]
     
   AVERAGE.EXE;6                 File ID:  (4098,149,0)
   Size:           36/36         Owner:    [DOCUMENTATION,MALCOLM]
   Created:  27-MAY-1996 12:22:26.30   
   Revised:  27-MAY-1996 12:22:51.35 (2)
   Expires:   <None specified>   
   Backup:    3-JUN-1996 22:03.09
   Effective: <None specified> 
   Recording: <None specified> 
   File organization:  Sequential
   Shelved state:      Online
   File attributes:    Allocation: 36, Extend: 36, Global buffer count: 0
                       No version limit
   Record format:      Variable length, maximum 255 bytes
   Record attributes:  Carriage return carriage control
   Journaling enabled: None
   File protection:    System:RWED, Owner:RWED, Group:RE, World:
   Access Cntrl List:  None
     
   Total of 1 file, 36/36 blocks.
     
   Directory DISK$DOCUMENT:[MALCOLM.TEST]
     
   AVERAGE.EXE;1                 File ID:  (7714,29,0)
   Size:           36/36         Owner:    [DOCUMENTATION,MALCOLM]
   Created:  15-APR-1996 10:12   
   Revised:  15-APR-1996 10:12 (1)
   Expires:   <None specified>   
   Backup:   15-APR-1996 22:41
   Effective: <None specified> 
   Recording: <None specified> 
   File organization:  Sequential
   Shelved state:      Shelved
   File attributes:    Allocation: 36, Extend: 36, Global buffer count: 0
                       No version limit
   Record format:      Variable length, maximum 255 bytes
   Record attributes:  Carriage return carriage control
   Journaling Enabled : None
   File protection:    System:RWED, Owner:RWED, Group:RE, World:
   Access Cntrl List:  None
      
   Total of 1 file, 36/36 blocks.
   Grand total of 2 directories, 2 files, 72/72 blocks.
   

   
   The DIRECTORY command in this example displays a full directory listing of one version of the AVERAGE.EXE file in the top-level directory [MALCOLM] and subdirectories under it.

9.3 Protecting Files

You can protect data on disk and magnetic tape media at the following levels:

Level of Protection	Description
Device level	For information on setting device protection characteristics, see the descriptions of the DCL commands INITIALIZE, MOUNT, SET DEVICES, SET SECURITY/PROTECTION, and SET VOLUME in Chapter 8 and in the OpenVMS DCL Dictionary. Refer to Chapter 7 for additional information about peripheral devices.
Volume level	The system provides protection for disk and tape volumes. For more information, see the following sections: Disk volume protection Section 8.4.1 Tape volume protection Section 8.4.2
File level	The system provides protection for disk files and directory files. For more information, see the following sections: Individual disk files Section 9.3.3 Directory files that reside on disk volumes Section 9.3.4

You can protect data residing on disk and tape volumes by using one or more of the following:

Type of Protection	For More Information
UIC-based protection codes	Chapter 11
Access control lists (ACLs)	Chapter 11
ISO 9660-formatted media protection	Section 8.4.2
ANSI-standard accessibility protection (magnetic tape only)	Section 8.4.2

For the most part, file protection is transparent. Tools exist, however, to adjust the protection of a file. You can set the protection or modify the ACL of a file if at least one of the following is true:

• You own the file.
• You have control access to the file.
• You have SYSPRV privilege.
• The group part of your UIC is less than or equal to MAXSYSGROUP.
• You have GRPPRV and you have the same group UIC as the file.

You can display ownership and protection information with the commands and qualifiers shown in Table 9-1.

Table 9-1 DCL Commands to Display Ownership and Protection

Command	Use to Display
DIRECTORY/ACL filespec	ACL of file
DIRECTORY/OWNER_UIC filespec	UIC of owner of file
DIRECTORY/PROTECTION filespec	UIC-based protection of file
DIRECTORY/SECURITY	All of the above
DIRECTORY/FULL filespec	All of the above and other, nonsecurity information
SHOW DEVICES/FULL device-name	Device UIC and protection
SHOW PROCESS	Process UIC
SHOW PROTECTION	Default file protection
SHOW SECURITY	All of the above

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  OSSG Documentation
  22-NOV-1996 14:21:54.25

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