Improving availability of a restartable staged storage data base system that uses logging facilities

A method for maintaining data availability in a data base system having backup and active processors, said system utilizing staged storage and logging facilities, comprising the steps by a backup processor of:

• (a) ascertaining the names and locations of the data set elements in staged storage which are updatable by the active processor, and upon the passing of control from a degraded active processor to the backup processor, logging the ascertained names and locations;
• (b) ascertaining whether the degraded active processor ceases to perform updates to staged storage;
• (c)upon the first reference to each data set element in staged storage by said backup processor, copying said referenced element to a buffer, diverting subsequent references from staged storage to the buffer copy, logging each update to said copy, the steps of copying, diverting, and logging being repeated until indication of said degraded active processor ceases to perform updates to staged storage;
• and
• (d) writing the buffer contents back to staged storage.