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When you want to retrieve data from the database, the fastest way to do this is if the data the query returns is already located in memory, or cache. If it is not located in cache, then the server pro...

Enabling Direct I/O Oracle provides a number of different ways of ensuring the performance of I/O write requests is optimal, including the use of direct I/O and asynchronous I/O (see below for more de...

This wait event will happen when all buffer gets have been suspended. This could happen when a file was read-only and is now read-write. All the existing buffers need to be invalidated since they are ...

This wait event only occurs when Flashback Database is turned on. A session waits for recovery writer (RVWR) to write flashback data to the flashback logs on disk because the buffers are full. Until R...

A direct path write I/O operation is just the opposite of the direct path read operation, and it writes buffers from a session's PGA to the datafiles. The direct path write operation allows a session ...

A direct path read I/O operation reads data into the session's PGA instead of the SGA. Direct read I/Os may be performed in synchronous or asynchronous mode, depending on the platform and the value of...

An Oracle session logs the db file sequential read wait event when it has to wait for a single-block I/O read request to complete. Oracle issues single-block I/O read requests when reading from indexe...

A Rollback Segment records the old values of data that were changed by each transaction, whether committed or not. The information in a rollback segment is used to: Generate read-consistent database ...

The db file scattered read wait event is similar to the db file sequential read, except that the session is waiting for a multi-block I/O read request to complete. The db file scattered read waits are...