Cache/disk file status indicator with data protection feature
US4506323A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Mar 3, 1982 |
| Grant date | Mar 19, 1985 |
| Priority date | — |
| Expiry date | Mar 3, 2002 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG06F12/0866
- WIPO fieldComputer technology
- WIPO sectorElectrical engineering
Abstract
A data processing system has a host processor, a RAM, a cache memory for storing segments of data, a plurality of disk drive devices and a storage control unit for controlling data transfers, data from the host processor being written to the cache memory and subsequently destaged to the disks. The storage control unit continuously updates a variable indicating the number of written-to segments resident in the cache memory that have not been destaged to the disks. The variable is stored in the RAM. A File Status flipflop is responsive to the variable to produce a "good file" signal when the variable is zero. The File Status flipflop is provided with an auxiliary power supply to maintain it in its present state in the event all power to the cache memory is terminated. Upon restoration of power after a complete power loss, the output of the status flipflop may be sampled by a command from the host processor to find out if any data was lost because written-to segments were present in the cache memory at the time all power was lost. The output of the File Status flipflop is also utilized to inhibit manually actuated functions which would destroy or invalidate written-to segments in the …
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.