Rcv               (VSAM)

DESCRIPTION
The "Rcv" flag indicates if an administrator has requested recovery protection 
for a specific "Dataset". Recovery protection is specified for a "Dataset" in
the Sun MTP File Control Table (FCT). 


VALUES
A "Dataset" with recovery protection displays 'Y', and a "Dataset" without it 
displays 'N'.


INTERPRETATION
When the recovery facility is active (see below) and requested for a particular
"Dataset", the Sun MTP system maintains before images for all updates to the 
"Dataset". If for some reason a transaction aborts, Sun MTP writes the before 
images back to the file  (a rollback), restoring the state of the data prior to 
the aborted transaction's execution. In other words, the recovery system, when 
activated and requested, maintains the database such that it is always in a 
consistent state.

If recovery is not requested for a "Dataset", Sun MTP does not maintain before 
images, even if the recovery facility is activated. In this case, Sun MTP does
not roll back an aborted transaction. If the aborted transaction issues writes 
prior to aborting, the data remains in the inconsistent state caused by the 
abort.


CONCLUSIONS
The recovery file is directly related to before images. To verify that before
images are actually being written to the recovery file for a specific dataset,
look for the "Dataset" in the Overview Screen's KxScrolledList. Then compare the
"Writes" field to the "B4 Images" field for that entry. Every write to the 
"Dataset" should be accompanied by a before image write to the recovery file.

If the system recovery facility is not turned on, Sun MTP cannot recover a 
particular "Dataset", regardless of the setting in the FCT. To turn the system
recovery facility on, the administrator must specify the name of the recovery
file with a size greater than 100 blocks in the Sun MTP VSAM Control Table (VCT).
The fields for the filename and number of blocks are located at the top of the 
VCT. Sun MTPScan's Recovery Screen shows the status of the system recovery facility.
