When a disk is more than 95% occupied, it is time to pay attention to it,
which is why it is shown in red.
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 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:
8
Mounted disks:
4
$1$DKA0:
Label:
ALPHA4_VMS84
Cluster size:
16
Size (MB):
17.783
Size (Blocks):
35566000
Used (MB):
17.762
Used (Blocks):
35523328
Percentage used:
99 %
Error Count:
0
Model:
COMPAQ RZ1ED
Structure:
ODS5
Rebuild needed:
No
Physical:
Sectors:
77
Tracks:
77
Cylinders:
5999
Miscellaneous:
Mount time:
14-APR-2025 14:48:03.06
Cache enabled:
TRUE
Highwater mark:
TRUE
Erase on delete:
FALSE
Current paths:
PKA0.0
Path responding:
FALSE
Disk analyze message
Number found
FUTCREDAT
38
FUTREVDAT
38
DELHEADER, file marked for DELETE
6
BADDIRENT
2
LOSTHEADER, file not found in a directory
2
FREESPADRIFT, free block count for this disk is incorrect