CHAPTER 19. DOSGEN COMMAND
19.3 Special Considerations
It is important to remember that on disk packs-for use with DOS systems recognizing more than one logical drive per physical disk pack, for example the 9370 and 9390 series disk systems, more then one DOSGEN must be done before the physical pack is fully initialized. This allows the user to DOSGEN any logical disk on the pack without disturbing files he wishes to keep that may be stored on other logical disks.
Another important thing to remember is that the 9370, 9380 and 9390 series disks must be formatted before DOSGEN can be used on them. Diskettes (for the 9380 series drives) come
pre-formatted from the manufacturer. A diskette that has been formatted with tracks locked out (error mapped) cannot be
DOSGENed. Disk packs for the 9370 and 9390 series drives do not have formatting when purchased. It is therefore necessary to
format all disk packs for the 9370 or 9390 series drives using the program INITDISK ~efore attempting to use DOSGEN on them.
The booted drive of a system cannot be DOSGENed. The disk from which DOSGEN is being run (usually the booted drive) should have COPY, CHAIN, and PUT IP L av ai lab Ie or the DOSGEN wi 11 not be able to complete correctly. Following surface verification DOSGEN enters a CHAIN procedure, which requires writing a CHAIN work
file. If the disk on which CHAIN resides is write protected, the processor will hang beeping until the protection is removed.
Since CHAIN is called during the DOSGEN process, this utility cannot be run using CHAINPLS.
19-2 DISK OPERATING SYSTEM
CHAPTER 20. DSKCHECK
20.1 Purpose
The purpose of DSKCHECK is to repair a logically damaged DOS volume. The performance of DOS is directly related to the
correctness of disk-resident sistem tables. DSKCHECK checks all system tables for format and content and is able to determine in most cases when an error in the system tables occurs, what the error is, and if the system tables can be reconstructed from the other data on the disk.
20.2 Use
DSKCHECK is invoked by entering:
DSKCHECK [<drivespec>][;<options>]
The drive specification may be entered as a standard drive s p e c i f i cat ion (: DO) or as a VOL I D (: PAY RO LL ) . I f no. d r i v e
specification is entered on the command line, the program will ask for one.
20.3 Options
The following options are available, and to be activated they must be entered on the command line.
"L" Option Local Printer On
-When set all messages will be printed on the local printer as well as displayed to the screen. An option conflict will be given if selected with
"s"
option."s"
Option Servo Printer On-When set all messages will be printed on the Servo printer as well as displayed to the screen. An option conflict will be given if selected with "L" option.
"F" Option System Fix Option
-Causes the program to compute the correct data when an error in System Data is detected, if this computation is possible, and allows the user to fix the data in error if he so chooses.
If an error in system data is detected, and the correct data can not be computed from the other pertinent usable data on the disk, the operator is so informed and may be asked if he wishes the file or entry deleted. All error correction messages contain a no changa option which will cause the program to continue to the next check without changing the data on the disk being checked.
This option is illegal and automatically deactivated if DSKCHECK is run from CHAIN, under ARC or under PS.
If no options are given the default is logging to the screen only and the fix option turned off.
20.4 System Tables and Data
Descriptions of the DOS tables, system data and their uses may be found in the chapter on System Structure.
All of the descriptions below are wri tten as if the "F" (fix) option were set. If this option is not active the operation is the same except that no request for corrective action is made if applicable.
20.5 Execution Phases
There are many execution phases in DSKCHECK, some of which are dependent on DOS type or previous condi tions and mayor may not be executed.
-20.5.1 Initialization
During initialization the program displays a signon message, and the option parameters are scanned. If the "F" (fix) option was selected the correction features are enabled. If the
(drivespec) is not specified on the command line it is asked for during this phase.
20-2 DISK OPERATING SYSTEM
20.5.2 HOI Checking
This phase of checking is dependent on the DOS on the disk being checked. It is not executed on DOS. C because thi s DOS does not use this technique of directory indexing. It uses Directory Mapping, which is verified during a later phase.
This phase reads the HDI (HASHED DIRECTORY INDEX) on the disk being checked, and compares the master to the backup. If an error occurs in reading either copy, or in comparing the copies, an
error message will be displayed, but no corrective action is allowed at this time. If no errors are detected an appropriate message is displayed.
20.5.3 CAT Checking
This phase of checking reads the CAT on the disk being checked and performs the same checks as described for HDI.
20.5.4 Directory Checking
During this phase each directory page is read and checked.
The master is compared to the backup copy, and if the pages do ·not match the entry affected is displayed. The program then asks
which entry should be retained, or if both entries should be deleted.
When an unsuccessful read occurs in either the master or backup, an error message is displayed and the comparison is not done. The good page is used to continue the checks. If both pages fail to read successfully an appropriate message is displayed and the next page is checked.
If. either or both pages read successfully, and when all compare errors are resolved, each entry is checked for valid format. If a de leted entry is encoun ter ed it is checked to see that the delete is complete. If it is not, an error message is displayed and the program asks if the error is to be corrected.
The RIB PDA is checked to see that it points to a valid 10 ca tion on the disk. If an err or is de te cted, an appro pr i ate message is displayed, and the program asks if the entry should be
del e ted. If t his en try is del e te d , no spa ce for it will be allocated in the computed CAT.
The program then proceeds by checking the filename/ext for
valid characters. Each character should fall into the range of A-Z or 0-9. If the program finds an invalid character, a warning message is displayed and the program continues.
Under DOS.C the program generates a mapping byte for each page as the page is checked. If the computed mapping byte does not match the mapping byte on the disk, a message is displayed and the computed mapping byte is entered into the computed CAT sector being generated.
20.5.5 RIB Checking
After all directory pages have been checked, the RIB for each entry in the directory is checked for format and space allocation validity. The RIB master and backup are first read and compared.
If either copy is not read successfully, the program asks if the good copy is to be written to the copy with the read failure. If a read failure occurs on both c6pies an error message will inform the user and the program will ask if the file is to be deleted.
No space will be allocated for that file in the computed CAT.
If a compare error is detected, the filename and the first 16 bytes of both copies are displayed and the program will ask which copy is to be retained on the disk.
After the RIB master and backup have been read and compared, and all errors resolved, the RIB format is checked for the correct PFN, LRN, and an 0377 in the 4th byte. Any format error detected will be displayed, and the corrective action requested.
Each segment descriptor is then checked" to see that it points to a valid location on the disk, and that the first sector of the segment has the proper PFN. The space allocation is computed and checked against the CAT and Lockout CAT for conflicts. If a
conflict occurs with the Lockout CAT the program will ask if the Lockout CAT is to be rewritten to free this space. "If a conflict
is detected with another file, the conflicting area is analyzed in the next two phases-and displayed with a request for action. If no conflicting areas are found the next two phases are skipped and the program continues with the Lockout CAT check.
20-4 DISK OPERATING SYSTEM
20.5.6 Cluster Allocation Phase 1
If a conflict was detected while checking the RIBs this phase is activated to reread all the good RIBs and find all other
conflicts.
20.5.7 Cluster Allocation Phase 2
Upon the determination of all conflicting clusters they are scanned to see which RIBs conflict and an opportunity to delete one or another or both conflicting files is given. If no change
is requested the CAT is updated with the conflicting clusters so there is protection from another file writing into this area.
20.5.8 Lock-out CAT Checking
If no change in the Lockout CAT has been made previously, it is now read and compared to its backup and checked against the CAT to see that all locked out space is also allocated in the CAT. If changes were made in previous phases of the program the generated Lockout CAT is checked against the CAT and if no errors are
detected it is written to the disk.
Any errors detected in this phase cause a descriptive message to be displayed and the program asks if a new Lockout CAT should be written. This new Lockout CAT, if written, will only have the space for the system tables locked out.