Starting automatic access to backup copies of objects

OAM can obtain a backup copy of an object if the primary copy of the object is resident on a removable media volume that is unavailable for any of the following reasons:

ALL: Is unavailable for any of the following reasons (nonspecific).
DB2ERROR: Encounters a DB2 error while attempting to retrieve the object data from the 4 KB, 32 KB, or LOB object storage table.
FSERROR: Encounters an error while attempting to retrieve the object data from a file system.
LOST: Is marked lost or is not-defined.
NOTOPER: Resides in a library that is marked nonoperational.
OFFLINE: Resides in a library that is offline, or pending offline.
UNREAD: Is marked unreadable (possibly due to damage or destruction).

With the use of the access backup function, it is unnecessary for the application to specify the VIEW=BACKUP1 or VIEW=BACKUP2 parameter to obtain the backup copy of the object.

Automatic access to backup copies of objects must be active for one or all of the specific reasons before OAM attempts to obtain the backup copy.

Restriction: This access to backup is limited to retrieval requests that are issued by the OSREQ macro. OSMC does not support access to backup for moving objects from removable media to the DB2 tables.

Take the following actions to ensure the retrieval of backup copies of objects. These actions can be performed any time, even when access backup is already active:

Make a physical inventory of the damaged removable media, noting the volumes residing on the unusable media.
Repair or replace the hardware as required.
Obtain all backup removable media volumes containing objects that are related to the objects on the damaged removable media.
Restore all the OAM DB2 databases from the latest image copy and complete forward recovery through the most recent updates that are available.
Use ISMF to make any necessary updates to the OAM configuration database for any alterations or updates that are needed for your hardware configuration.
Use the F OAM,UPDATE,VOLUME,volser command to alter the VOLUME table or Tape Volume table in the OCDB, changing the READABLE column value to "N" (NO) for each pair of volumes that is identified as residing on damaged (unreadable) media.

Performing one or more of these steps allows normal application processing to occur until object recovery operations restore the primary copies of objects.

For more information on this function, see Accessing backup objects automatically.

The following MVS command syntax starts the automatic access to backup copies function:


>>-+-MODIFY-+--------------------------------------------------->
   '-F------'   

                         .-UNREAD --.   .-BACKUP1-.   
>--OAM,-+-START-+-,-AB-,-+----------+-,-+---------+------------><
        '-S-----'        +-ALL------+   '-BACKUP2-'   
                         +-DB2ERROR-+                 
                         +-FSERROR--+                 
                         +-LOST-----+                 
                         +-NOTOPER--+                 
                         '-OFFLINE--'

To start processing for the automatic access to backup copies function:

Enter the following command:
```
F OAM,START,AB,reason,BACKUP1 | BACKUP2
```
The following are valid values and descriptions for the reason keyword:
ALL

When a retrieve for an object is attempted and the optical or tape volume on which the object resides is not available for any of the following reasons, the backup copy of the object is retrieved.

DB2ERROR

If a DB2 error occurs while OAM is retrieving object data from the 4 KB, 32 KB, or LOB object storage table and the first or second backup copy exists, OAM retrieves the object data from the backup copy. This function allows access to backup copies of objects that reside on removable media (optical or tape) when the DB2 resident data is unavailable, such as during the recovery of DB2 tables.
Restriction: The object directory entry is necessary for OAM to proceed with any object request. If a DB2 error occurs while OAM attempts to retrieve the object directory entry, OAM does not retrieve the backup copy of the object. Without the object directory information, OAM cannot determine the primary or backup location of the object.

FSERROR

If a file system error occurs while OAM is retrieving object data from the file system and the first or second backup copy exists, OAM retrieves the object from the backup copy. This function allows access to backup copies of objects that reside on removable media (optical or tape) when the file system resident data is unavailable (because, for example, the file system is unmounted or undergoing maintenance procedures such as backup of the file system data).

LOST

When a retrieve for an object is attempted, and the optical or tape volume on which the object resides is marked lost or is not-defined, the backup copy of the object is retrieved.

NOTOPER

When a retrieve for an object is attempted and the optical or tape volume on which the object resides is in a library that is marked nonoperational, the backup copy of the object is retrieved.

OFFLINE

When a retrieve for an object is attempted and the optical or tape volume on which the object resides is in a library that is offline or pending offline, the backup copy of the object is retrieved.

UNREAD

UNREAD is the default. When a retrieve for an object is attempted and the optical or tape volume on which the object resides is marked not readable, the backup copy of the object is retrieved.

The following are the valid, optional parameters for specifying which backup copy should be accessed:
BACKUP1 | BACKUP2

When a primary copy of an object that is read by an application is not available for the specified reason, and BACKUP1 is specified on the START command for automatic access to backup, an attempt is made to retrieve the object from the first backup copy of the object. If BACKUP2 is specified, an attempt is made to retrieve the object from the second backup copy of the object. BACKUP1 is the default if neither BACKUP1 nor BACKUP2 is specified.

_______________________________________________________
The system issues the following message:
```
CBR1000I OAM START command execution scheduled.
```
_______________________________________________________
Once the access backup processing starts, the system issues the following message:
```
CBR1090I OAM Access Backup processing started for reason 
using the {1st | 2nd} backup copy.
```
Where reason can be one of the following values:
- DB2 OBJECT TABLE ERRORS
- FILE SYSTEM ERRORS
- LOST VOLUMES
- NOT OPERATIONAL LIBRARIES
- OFFLINE LIBRARIES
- UNREADABLE VOLUMES
_______________________________________________________
Access backup processing remains active until a STOP,AB,reason command is issued. The system issues the following message:
```
CBR1091I OAM Access Backup processing stopped for reason.
```
_______________________________________________________
If access backup processing is active and the operator tries to issue another START,AB,reason command, the system issues the following message:
```
CBR1092I OAM Access Backup processing already started for reason
using the [1st | 2nd] backup copy.
```
_______________________________________________________

The following is a sample of enabling Access Backup for UNREADABLE VOLUMES with the optional parameter BACKUP2 specified:

F OAM,START,AB,UNREAD,BACKUP2    
                    
CBR1000I OAM START command execution scheduled.      
CBR1090I OAM Access Backup processing started for UNREADABLE VOLUMES using the 
             2nd backup copy.

Note: If no automatic access to backup keywords have been specified on the SETOPT statement in the CBROAMxx parmlib member, then stopping OAM and starting OAM does not affect the status of automatic access to backup. If access to backup has been started and OAM is stopped, access to backup is active when OAM is started again.

Note: You can also configure automatic access to backup in the CBROAMxx PARMLIB SETOPT statement using keywords which follow very closely the convention that the MODIFY OAM,START,AB command uses.