Checkpointing in Oracle
Ashok Joshi, William J. Bridge, Juan Loaiza, Tirthankar Lahiri · 1998
Checkpointing is an important mechanism for limiting crash recovery times. This paper describes a new checkpointing algorithm that was implemented in Oracle 8.0. This algorithm efJiciently JWS buffers which need to be written for checkpointing and easily scales to very large buffer cache sizes: it has been tested with buffer caches as large as six million buffers. Based on this algorithm, we have implemented a new checkpointing mechanism which we refer to as the incremental checkpointing mechanism. Incre-mental checkpoints are continuous, low overhead checkpoints that wn’te buffers as a background activity. Incremental checkpointing is able to continuously advance the database checkpoint, i.e., the starting position in the redo log for crash recovery, resulting in dramatic improvements in recovery time while imposing minimal overhead during normal processing. The rate of bu$er writes for incremental checkpointing can be con-trolled by the user to balance checkpoint writing overhead with recovery time requirements. In this paper; we describe the new data structures and algorithms that have been implemented for checkpointing and for incremental checkpointing