DSKRAT Jun73

DSKRAT is a "Disk File Damage Assessment Program" for Level D disk file structures, dating back to 1973. Its primary function is to scan a file system to identify and report inconsistencies and errors.

Here's a summary of its key features and operation:

1. Purpose: To assess the integrity of disk file structures by detecting damage and inconsistencies.
2. Operation:
   • Requires "super USETI" privileges to run.
   • Scans the file structure, reads and verifies Record Information Blocks (RIBs) and checksums data groups.
   • Constructs its own "computed System Allocation Table" (SAT) and compares it against the actual disk's SAT.
   • Reports any discrepancies between its computed SAT and the disk's SAT.
3. Detected Inconsistencies:
   • Clusters allocated to multiple files ("MULTIPLY-USED").
   • Clusters used by a file but not marked as allocated in the disk SAT.
   • Clusters marked as allocated in the disk SAT but not assigned to any file.
   • Errors in RIBs or checksums.
4. Two-Pass System:
   • Pass 1: Performs a general scan, identifying most file structure issues and printing a list of problematic clusters.
   • Pass 2: If "multiply-used" clusters are detected in Pass 1, a second pass is initiated specifically to generate an error line for each file claiming such clusters. If no multiply-used clusters are found, Pass 2 is skipped.
5. Output: All detected errors and summary information are directed to the LPT device (typically a printer).
6. Caveat: The document notes that if other users are actively referencing (writing or deleting files) the disks during DSKRAT's operation, the SAT blocks read might not be current, potentially leading to spurious errors, though true errors should still be identified.