The more often checkpoints are taken the fewer log records that have to be read and the fewer undos and redos that must be accomplished when recovering from a system crash. Checkpoints have no effect on recovery from a disk crash because we have to process all log records back to the most recent anyway. Compare the shadow paging recovery scheme with the log-based recovery schemes in terms of ease of implementation and overhead cost. Shadow paging is easier to implement. Time overhead depends on the size of the page table as compared to the average total size of the log records written for a single transaction.
Space overhead depends on the size of the page table as compared to the size of the log file.
Presumably a log file would take much more stable storage space than two copies of the page table. Show a possible physical ordering of the blocks after the following updates, assuming that shadow paging is used, and the buffer in main memory can hold 3 blocks, and a LRU buffer management strategy is used. 1. read block 3 2. If that is true then any physical ordering is possible both before and after the updates are performed.