Backup-while-open (BWO)

The BWO facility, together with other system facilities and products, allows you to take a backup copy of a VSAM data set while it remains open for update.

Many CICS® applications depend on their data sets being open for update over a long period of time. Normally, you cannot take a backup of the data set while the data set is open. Thus, if a failure occurs that requires forward recovery, all updates that have been made to the data set since it was opened must be recovered. This means that you must keep all forward recovery logs that have been produced since the data set was opened. A heavily used data set that has been open for update for several days or weeks might need much forward recovery.

Using BWO, only the updates that have been made since the last backup copy was taken need to be recovered. This could considerably reduce the amount of forward recovery that is needed.