Dirty Pages Table

This table is used to represent information about dirty buffer pages during normal processing. It is also used during restart recovery.It is implemented using hashing or via the deferred- writes queue mechanism. Each entry in the table consists of 2 fields :

1. PageID and
2. RecLSN

During normal processing , when a non-dirty page is being fixed in the buffers with the intention to modify , the buffer manager records in the buffer pool (BP) dirty-pages table , as RecLSN , the current end-of-log LSN , which will be the LSN of the next log record to be written. The value of RecLSN indicates from what point in the log there may be updates. Whenever pages are written back to nonvolatile storage , the corresponding entries in the BP dirty-page table are removed. The contents of this table are included in the checkpoint record that is written during normal processing. The restart dirty-pages table is initialized from the latest checkpoint's record and is modified during the analysis of the other records during the analysis pass. The minimum RecLSN value in the table gives the starting point for the redo pass during restart recovery.