Managing a redundant computerized database using a replicated database cache

A redundant database server apparatus, comprising:

• a first database server having at least one first processor and a first memory;
• a second database server having at least one second processor and a second memory;
• a first database manager embodied as computer programming code recorded on non-transitory computer-readable media, said computer programming code executable on the at least one first processor and storable in the first memory, said first database manager:
• (a) performing a plurality of accesses to a shared database on behalf of respective clients, wherein at least some of said plurality of accesses perform updates to data in said shared database, said first database manager logging updates to said shared database in a sequential database log, and
• (b) causing data from a database cache in said first memory to be copied to a corresponding database cache in said second memory concurrently with performing a plurality of accesses to said shared database on behalf of respective clients, wherein said database cache in said first memory occupies a first range of virtual address space in said first database server, and said corresponding database cache in said second memory occupies a second range of virtual address space in said second database server, said first and second ranges being identical, and wherein said data from the database cache in said first memory is copied to the corresponding database cache in said second memory concurrently with performing the a plurality of accesses to said shared database on behalf of respective clients by copying each item of data from a respective virtual address in the database cache in said memory to an identical respective virtual address in the corresponding database cache in said second memory;
• a second database manager embodied as computer programming code recorded on non-transitory computer-readable media, said computer programming code executable on the at least one second processor and storable in the second memory, said second database manager:
• (a) responsive to receiving an indication that a failure has occurred in said first database server, recovering the database to a consistent state in said second database server by:
• (i) using said sequential database log to verify selective data from said database cache in said second memory, and (ii) using the selective verified data from said database cache in said second memory to recover the database to a consistent state;
• and
• (b) thereafter operating said second database server to perform a plurality of accesses to said shared database on behalf of respective clients.