Volume shadowing performsfour basic functions. The two most important, as with any disk I/Osubsystem, are to satisfy read and write requests. The other twofunctions, copy and merge, are required for shadow set maintenance.
Copy and merge operations are the cornerstone of achievingdata availability. Under certain circumstances, Volume Shadowingfor OpenVMS must perform a copy or a merge operation to ensure thatcorresponding LBNs on all shadow set members contain the same information.Although volume shadowing automatically performs these operations,this chapter provides an overview of their operation.
Copy and merge operations occur at the same time that applicationsand user processes read and write to active shadow set members,thereby having a minimal effect on current application processing.
HP Volume Shadowing for OpenVMS
