In OpenVMS, the Highwater Mark (HWM) for a disk refers to the highest block number that has ever been
written to on that disk. It is a critical concept for disk space management and security.
Definition:
- The HWM indicates the furthest point (in blocks) where data has been written on the disk.
- Any blocks below the HWM are considered to have potentially contained data at some point.
- Any blocks above the HWM are guaranteed to be unused (never written).
Purpose:
- Ensures that deleted or overwritten files cannot be recovered from disk areas that have been reallocated.
- Helps prevent unauthorized access to old data by ensuring new allocations occur only above the HWM.
How It Works:
- When a file is deleted, its space is freed, but the data remains until overwritten.
- OpenVMS ensures that new file allocations occur at or above the HWM, preventing accidental exposure of old data.
- The HWM only moves forward (increases) as new data is written.
Conclusion:
The Highwater Mark in OpenVMS is a safeguard to ensure disk security and efficient space management by tracking the
highest block ever written.
This prevents residual data exposure and helps maintain system integrity.
Disk Erase on Delete
Erase on Delete is a security feature in OpenVMS that ensures deleted files are securely overwritten,
preventing potential recovery of sensitive data.
How It Works
When enabled, this feature:
- Overwrites the file's data blocks with a pattern (typically zeros or random data) when the file is deleted
- Then removes the file's directory entry
This is different from standard file deletion where only the directory entry is removed while the actual data
remains on disk until overwritten by new files.
Implementation
There are several ways to implement Erase on Delete in OpenVMS:
- System-wide setting: Can be enabled with: $ SET SECURITY/CLASS=VOLUME/ERASE_ON_DELETE device:
- For specific files: Can be set with: $ SET FILE/ERASE_ON_DELETE filename
- Directory default: Can be set so all files created in a directory inherit this attribute: $ SET DIRECTORY/ERASE_ON_DELETE dirname
Importance
This feature is particularly important for:
- Systems handling sensitive data
- Compliance with data protection regulations
- Preventing data leakage when storage media is reused or discarded
Disk High Water Mark
In OpenVMS, the Highwater Mark (HWM) for a disk refers to the highest block number that has ever been
written to on that disk. It is a critical concept for disk space management and security.
Definition:
- The HWM indicates the furthest point (in blocks) where data has been written on the disk.
- Any blocks below the HWM are considered to have potentially contained data at some point.
- Any blocks above the HWM are guaranteed to be unused (never written).
Purpose:
- Ensures that deleted or overwritten files cannot be recovered from disk areas that have been reallocated.
- Helps prevent unauthorized access to old data by ensuring new allocations occur only above the HWM.
How It Works:
- When a file is deleted, its space is freed, but the data remains until overwritten.
- OpenVMS ensures that new file allocations occur at or above the HWM, preventing accidental exposure of old data.
- The HWM only moves forward (increases) as new data is written.
Conclusion:
The Highwater Mark in OpenVMS is a safeguard to ensure disk security and efficient space management by tracking the
highest block ever written.
This prevents residual data exposure and helps maintain system integrity.
Disk Erase on Delete
Erase on Delete is a security feature in OpenVMS that ensures deleted files are securely overwritten,
preventing potential recovery of sensitive data.
How It Works
When enabled, this feature:
- Overwrites the file's data blocks with a pattern (typically zeros or random data) when the file is deleted
- Then removes the file's directory entry
This is different from standard file deletion where only the directory entry is removed while the actual data
remains on disk until overwritten by new files.
Implementation
There are several ways to implement Erase on Delete in OpenVMS:
- System-wide setting: Can be enabled with: $ SET SECURITY/CLASS=VOLUME/ERASE_ON_DELETE device:
- For specific files: Can be set with: $ SET FILE/ERASE_ON_DELETE filename
- Directory default: Can be set so all files created in a directory inherit this attribute: $ SET DIRECTORY/ERASE_ON_DELETE dirname
Importance
This feature is particularly important for:
- Systems handling sensitive data
- Compliance with data protection regulations
- Preventing data leakage when storage media is reused or discarded
Disk High Water Mark
In OpenVMS, the Highwater Mark (HWM) for a disk refers to the highest block number that has ever been
written to on that disk. It is a critical concept for disk space management and security.
Definition:
- The HWM indicates the furthest point (in blocks) where data has been written on the disk.
- Any blocks below the HWM are considered to have potentially contained data at some point.
- Any blocks above the HWM are guaranteed to be unused (never written).
Purpose:
- Ensures that deleted or overwritten files cannot be recovered from disk areas that have been reallocated.
- Helps prevent unauthorized access to old data by ensuring new allocations occur only above the HWM.
How It Works:
- When a file is deleted, its space is freed, but the data remains until overwritten.
- OpenVMS ensures that new file allocations occur at or above the HWM, preventing accidental exposure of old data.
- The HWM only moves forward (increases) as new data is written.
Conclusion:
The Highwater Mark in OpenVMS is a safeguard to ensure disk security and efficient space management by tracking the
highest block ever written.
This prevents residual data exposure and helps maintain system integrity.
Disk Erase on Delete
Erase on Delete is a security feature in OpenVMS that ensures deleted files are securely overwritten,
preventing potential recovery of sensitive data.
How It Works
When enabled, this feature:
- Overwrites the file's data blocks with a pattern (typically zeros or random data) when the file is deleted
- Then removes the file's directory entry
This is different from standard file deletion where only the directory entry is removed while the actual data
remains on disk until overwritten by new files.
Implementation
There are several ways to implement Erase on Delete in OpenVMS:
- System-wide setting: Can be enabled with: $ SET SECURITY/CLASS=VOLUME/ERASE_ON_DELETE device:
- For specific files: Can be set with: $ SET FILE/ERASE_ON_DELETE filename
- Directory default: Can be set so all files created in a directory inherit this attribute: $ SET DIRECTORY/ERASE_ON_DELETE dirname
Importance
This feature is particularly important for:
- Systems handling sensitive data
- Compliance with data protection regulations
- Preventing data leakage when storage media is reused or discarded
Disk High Water Mark
In OpenVMS, the Highwater Mark (HWM) for a disk refers to the highest block number that has ever been
written to on that disk. It is a critical concept for disk space management and security.
Definition:
- The HWM indicates the furthest point (in blocks) where data has been written on the disk.
- Any blocks below the HWM are considered to have potentially contained data at some point.
- Any blocks above the HWM are guaranteed to be unused (never written).
Purpose:
- Ensures that deleted or overwritten files cannot be recovered from disk areas that have been reallocated.
- Helps prevent unauthorized access to old data by ensuring new allocations occur only above the HWM.
How It Works:
- When a file is deleted, its space is freed, but the data remains until overwritten.
- OpenVMS ensures that new file allocations occur at or above the HWM, preventing accidental exposure of old data.
- The HWM only moves forward (increases) as new data is written.
Conclusion:
The Highwater Mark in OpenVMS is a safeguard to ensure disk security and efficient space management by tracking the
highest block ever written.
This prevents residual data exposure and helps maintain system integrity.
Disk Erase on Delete
Erase on Delete is a security feature in OpenVMS that ensures deleted files are securely overwritten,
preventing potential recovery of sensitive data.
How It Works
When enabled, this feature:
- Overwrites the file's data blocks with a pattern (typically zeros or random data) when the file is deleted
- Then removes the file's directory entry
This is different from standard file deletion where only the directory entry is removed while the actual data
remains on disk until overwritten by new files.
Implementation
There are several ways to implement Erase on Delete in OpenVMS:
- System-wide setting: Can be enabled with: $ SET SECURITY/CLASS=VOLUME/ERASE_ON_DELETE device:
- For specific files: Can be set with: $ SET FILE/ERASE_ON_DELETE filename
- Directory default: Can be set so all files created in a directory inherit this attribute: $ SET DIRECTORY/ERASE_ON_DELETE dirname
Importance
This feature is particularly important for:
- Systems handling sensitive data
- Compliance with data protection regulations
- Preventing data leakage when storage media is reused or discarded
Disk Rebuild is Recommmended
A rebuild for disk $1$DKA400: is recommended.
The cause of this is often a system crash and a MOUNT/NOREBUILD
executed during the startup of OpenVMS.
To rebuild the disk, either use:
SET VOLUME/REBUILD $1$DKA400:
or
Dismount the volume, and mount the volume again using MOUNT/REBUILD $1$DKA400:.
Disk High Water Mark
In OpenVMS, the Highwater Mark (HWM) for a disk refers to the highest block number that has ever been
written to on that disk. It is a critical concept for disk space management and security.
Definition:
- The HWM indicates the furthest point (in blocks) where data has been written on the disk.
- Any blocks below the HWM are considered to have potentially contained data at some point.
- Any blocks above the HWM are guaranteed to be unused (never written).
Purpose:
- Ensures that deleted or overwritten files cannot be recovered from disk areas that have been reallocated.
- Helps prevent unauthorized access to old data by ensuring new allocations occur only above the HWM.
How It Works:
- When a file is deleted, its space is freed, but the data remains until overwritten.
- OpenVMS ensures that new file allocations occur at or above the HWM, preventing accidental exposure of old data.
- The HWM only moves forward (increases) as new data is written.
Conclusion:
The Highwater Mark in OpenVMS is a safeguard to ensure disk security and efficient space management by tracking the
highest block ever written.
This prevents residual data exposure and helps maintain system integrity.
Disk Erase on Delete
Erase on Delete is a security feature in OpenVMS that ensures deleted files are securely overwritten,
preventing potential recovery of sensitive data.
How It Works
When enabled, this feature:
- Overwrites the file's data blocks with a pattern (typically zeros or random data) when the file is deleted
- Then removes the file's directory entry
This is different from standard file deletion where only the directory entry is removed while the actual data
remains on disk until overwritten by new files.
Implementation
There are several ways to implement Erase on Delete in OpenVMS:
- System-wide setting: Can be enabled with: $ SET SECURITY/CLASS=VOLUME/ERASE_ON_DELETE device:
- For specific files: Can be set with: $ SET FILE/ERASE_ON_DELETE filename
- Directory default: Can be set so all files created in a directory inherit this attribute: $ SET DIRECTORY/ERASE_ON_DELETE dirname
Importance
This feature is particularly important for:
- Systems handling sensitive data
- Compliance with data protection regulations
- Preventing data leakage when storage media is reused or discarded
Disk Rebuild is Recommmended
A rebuild for disk $1$DKA500: is recommended.
The cause of this is often a system crash and a MOUNT/NOREBUILD
executed during the startup of OpenVMS.
To rebuild the disk, either use:
SET VOLUME/REBUILD $1$DKA500:
or
Dismount the volume, and mount the volume again using MOUNT/REBUILD $1$DKA500:.
Disk High Water Mark
In OpenVMS, the Highwater Mark (HWM) for a disk refers to the highest block number that has ever been
written to on that disk. It is a critical concept for disk space management and security.
Definition:
- The HWM indicates the furthest point (in blocks) where data has been written on the disk.
- Any blocks below the HWM are considered to have potentially contained data at some point.
- Any blocks above the HWM are guaranteed to be unused (never written).
Purpose:
- Ensures that deleted or overwritten files cannot be recovered from disk areas that have been reallocated.
- Helps prevent unauthorized access to old data by ensuring new allocations occur only above the HWM.
How It Works:
- When a file is deleted, its space is freed, but the data remains until overwritten.
- OpenVMS ensures that new file allocations occur at or above the HWM, preventing accidental exposure of old data.
- The HWM only moves forward (increases) as new data is written.
Conclusion:
The Highwater Mark in OpenVMS is a safeguard to ensure disk security and efficient space management by tracking the
highest block ever written.
This prevents residual data exposure and helps maintain system integrity.
Disk Erase on Delete
Erase on Delete is a security feature in OpenVMS that ensures deleted files are securely overwritten,
preventing potential recovery of sensitive data.
How It Works
When enabled, this feature:
- Overwrites the file's data blocks with a pattern (typically zeros or random data) when the file is deleted
- Then removes the file's directory entry
This is different from standard file deletion where only the directory entry is removed while the actual data
remains on disk until overwritten by new files.
Implementation
There are several ways to implement Erase on Delete in OpenVMS:
- System-wide setting: Can be enabled with: $ SET SECURITY/CLASS=VOLUME/ERASE_ON_DELETE device:
- For specific files: Can be set with: $ SET FILE/ERASE_ON_DELETE filename
- Directory default: Can be set so all files created in a directory inherit this attribute: $ SET DIRECTORY/ERASE_ON_DELETE dirname
Importance
This feature is particularly important for:
- Systems handling sensitive data
- Compliance with data protection regulations
- Preventing data leakage when storage media is reused or discarded
Disk High Water Mark
In OpenVMS, the Highwater Mark (HWM) for a disk refers to the highest block number that has ever been
written to on that disk. It is a critical concept for disk space management and security.
Definition:
- The HWM indicates the furthest point (in blocks) where data has been written on the disk.
- Any blocks below the HWM are considered to have potentially contained data at some point.
- Any blocks above the HWM are guaranteed to be unused (never written).
Purpose:
- Ensures that deleted or overwritten files cannot be recovered from disk areas that have been reallocated.
- Helps prevent unauthorized access to old data by ensuring new allocations occur only above the HWM.
How It Works:
- When a file is deleted, its space is freed, but the data remains until overwritten.
- OpenVMS ensures that new file allocations occur at or above the HWM, preventing accidental exposure of old data.
- The HWM only moves forward (increases) as new data is written.
Conclusion:
The Highwater Mark in OpenVMS is a safeguard to ensure disk security and efficient space management by tracking the
highest block ever written.
This prevents residual data exposure and helps maintain system integrity.
Disk Erase on Delete
Erase on Delete is a security feature in OpenVMS that ensures deleted files are securely overwritten,
preventing potential recovery of sensitive data.
How It Works
When enabled, this feature:
- Overwrites the file's data blocks with a pattern (typically zeros or random data) when the file is deleted
- Then removes the file's directory entry
This is different from standard file deletion where only the directory entry is removed while the actual data
remains on disk until overwritten by new files.
Implementation
There are several ways to implement Erase on Delete in OpenVMS:
- System-wide setting: Can be enabled with: $ SET SECURITY/CLASS=VOLUME/ERASE_ON_DELETE device:
- For specific files: Can be set with: $ SET FILE/ERASE_ON_DELETE filename
- Directory default: Can be set so all files created in a directory inherit this attribute: $ SET DIRECTORY/ERASE_ON_DELETE dirname
Importance
This feature is particularly important for:
- Systems handling sensitive data
- Compliance with data protection regulations
- Preventing data leakage when storage media is reused or discarded
Disk Rebuild is Recommmended
A rebuild for disk $1$LDA1: is recommended.
The cause of this is often a system crash and a MOUNT/NOREBUILD
executed during the startup of OpenVMS.
To rebuild the disk, either use:
SET VOLUME/REBUILD $1$LDA1:
or
Dismount the volume, and mount the volume again using MOUNT/REBUILD $1$LDA1:.
Disk High Water Mark
In OpenVMS, the Highwater Mark (HWM) for a disk refers to the highest block number that has ever been
written to on that disk. It is a critical concept for disk space management and security.
Definition:
- The HWM indicates the furthest point (in blocks) where data has been written on the disk.
- Any blocks below the HWM are considered to have potentially contained data at some point.
- Any blocks above the HWM are guaranteed to be unused (never written).
Purpose:
- Ensures that deleted or overwritten files cannot be recovered from disk areas that have been reallocated.
- Helps prevent unauthorized access to old data by ensuring new allocations occur only above the HWM.
How It Works:
- When a file is deleted, its space is freed, but the data remains until overwritten.
- OpenVMS ensures that new file allocations occur at or above the HWM, preventing accidental exposure of old data.
- The HWM only moves forward (increases) as new data is written.
Conclusion:
The Highwater Mark in OpenVMS is a safeguard to ensure disk security and efficient space management by tracking the
highest block ever written.
This prevents residual data exposure and helps maintain system integrity.
Disk Erase on Delete
Erase on Delete is a security feature in OpenVMS that ensures deleted files are securely overwritten,
preventing potential recovery of sensitive data.
How It Works
When enabled, this feature:
- Overwrites the file's data blocks with a pattern (typically zeros or random data) when the file is deleted
- Then removes the file's directory entry
This is different from standard file deletion where only the directory entry is removed while the actual data
remains on disk until overwritten by new files.
Implementation
There are several ways to implement Erase on Delete in OpenVMS:
- System-wide setting: Can be enabled with: $ SET SECURITY/CLASS=VOLUME/ERASE_ON_DELETE device:
- For specific files: Can be set with: $ SET FILE/ERASE_ON_DELETE filename
- Directory default: Can be set so all files created in a directory inherit this attribute: $ SET DIRECTORY/ERASE_ON_DELETE dirname
Importance
This feature is particularly important for:
- Systems handling sensitive data
- Compliance with data protection regulations
- Preventing data leakage when storage media is reused or discarded
Disk Information
Number of disks:
16
Mounted disks:
8
DSA0:
Label:
DISK10
Cluster size:
16
Size (MB):
17.783
Size (Blocks):
35566000
Used (MB):
11.752
Used (Blocks):
23503824
Percentage used:
66 %
Error Count:
0
Model:
Shadow set
Structure:
ODS5
Rebuild needed:
No
Physical:
Sectors:
77
Tracks:
77
Cylinders:
5999
Miscellaneous:
Cache enabled:
TRUE
Highwater mark:
TRUE
Erase on delete:
FALSE
Current paths:
NOT Available
Path responding:
NOT Available
Member:
$1$DKA0:
(DEC RZ1DB)
DSA1:
Label:
DISK13
Cluster size:
16
Size (MB):
8.886
Size (Blocks):
17773524
Used (MB):
4.198
Used (Blocks):
8396308
Percentage used:
47 %
Error Count:
0
Model:
Shadow set
Structure:
ODS5
Rebuild needed:
No
Physical:
Sectors:
64
Tracks:
65
Cylinders:
4273
Miscellaneous:
Mount time:
24-FEB-2025 12:27:11.54
Cache enabled:
FALSE
Highwater mark:
TRUE
Erase on delete:
FALSE
Current paths:
NOT Available
Path responding:
NOT Available
Members:
$1$DKA300:
(DEC RZ1DB)
$1$DKC300:
(COMPAQ RZ1ED)
Disk analyze message
Number found
FREESPADRIFT, free block count for this disk is incorrect
1
DSA2:
Label:
DISK11
Cluster size:
16
Size (MB):
4.190
Size (Blocks):
8380080
Used (MB):
1.992
Used (Blocks):
3982528
Percentage used:
47 %
Error Count:
0
Model:
Shadow set
Structure:
ODS5
Rebuild needed:
No
Physical:
Sectors:
54
Tracks:
53
Cylinders:
2929
Miscellaneous:
Cache enabled:
FALSE
Highwater mark:
TRUE
Erase on delete:
FALSE
Current paths:
NOT Available
Path responding:
NOT Available
Member:
$1$DKA100:
(DEC RZ1DB)
Disk analyze message
Number found
DELHEADER, file marked for DELETE
5
LOSTHEADER, file not found in a directory
3
DSA3:
Label:
DISK12
Cluster size:
16
Size (MB):
4.190
Size (Blocks):
8380080
Used (MB):
2.151
Used (Blocks):
4300208
Percentage used:
51 %
Error Count:
0
Model:
Shadow set
Structure:
ODS5
Rebuild needed:
No
Physical:
Sectors:
54
Tracks:
53
Cylinders:
2929
Miscellaneous:
Mount time:
24-FEB-2025 12:27:12.85
Cache enabled:
FALSE
Highwater mark:
TRUE
Erase on delete:
FALSE
Current paths:
NOT Available
Path responding:
NOT Available
Member:
$1$DKC400:
(COMPAQ RZ1ED)
Disk analyze message
Number found
BADHIGHWATER, inconsistent highwater mark and EFBLK