What is direct path read in AWR report?

A direct read is a physical I/O from a data file that bypasses the buffer cache and reads the data block directly into process-private memory. If asynchronous I/O is supported (and in use), then Oracle can submit I/O requests and continue processing.

What is direct path read temp in Oracle?

The Direct Path Read Temp wait events are an access path in which multiple Oracle blocks are read directly to the Oracle process memory without being read into the buffer cache in the Shared Global Area (SGA). in Direct Path Read Temp the data is read from temporary tablespaces.

What is direct path write in Oracle?

Direct path writes allow a session to queue an I/O write request and continue processing while the OS handles the I/O. If the session needs to know if an outstanding write is complete, then it waits for this wait event.

What is DB file scattered read?

A db file scattered read issues a scatter-read to read the data into multiple discontinuous memory locations. A scattered read is usually a multiblock read. It can occur for a fast full scan (of an index) in addition to a full table scan.

What is _serial_direct_read?

The _serial_direct_read parameter controls the direct path read decision both for table and index segment scans.

What is DB file sequential read in Oracle?

“The db file sequential read Oracle metric event signifies that the user process is reading buffers into the SGA buffer cache and is waiting for a physical I/O call to return. This call differs from a scattered read, because a sequential read is reading data into contiguous memory space.

What is disk file operations I O?

This event is used to wait for disk file operations (for example, open, close, seek, and resize). It is also used for miscellaneous I/O operations such as block dumps and password file accesses.

How do I fix a scattered read database?

The cure for the db file scattered read waits is the same as the one for the db file sequential read: find and tune the SQL statement that clocked the most time on the event. The goal of tuning is also to minimize the number of logical and physical I/Os. Follow the examples in the db file sequential read event section.

How do I use Smart Scan Exadata?

In Exadata, SQL processing is divided and also takes place on the storage tier.

Tradition SQL processing.
Exadata server SQL processing.
Step 1: Connect to database.
Step 2: Verify statistics.
Step 3: Execute a select query with Smart Scan disabled.
Step 4: Verify statistics again.
Step 5: Reset the statistics.

What is cell smart table scan?

This means you are using your exadata how it’s intended to be used, which means your full table scan is offloaded to the cells (storage layer), and potentially all kinds of optimisations are happening, like column filtering, predicate filtering, storage indexing, etc. …