How can I improve db file sequential read?

There are two things you can do to minimize the db file sequential read waits:

1. Optimize the SQL statement that initiated most of the waits by reducing the number of physical and logical reads.
2. Reduce the average wait time.

What is db file sequential read?

The db file sequential read event signifies that the user process is reading data into the SGA buffer cache and is waiting for a physical I/O call to return. It corresponds to a single-block read. Single block I/Os are usually the result of using indexes.

What is the difference between db file sequential and scattered reads?

A db file sequential read is an event that shows a wait for a foreground process while doing a sequential read from the database. A db file scattered read is the same type of event as “db file sequential read”, except that Oracle will read multiple data blocks. Multi-block reads are typically used on full table scans.

What is control file sequential read in Oracle?

The control file sequential read Oracle metric indicates the process is waiting for blocks to be read from a control file. This happens in many cases. For example, while: making a backup of the controlfiles. sharing information (between instances) from the controlfile.

What is sequential read in SAP?

A “Sequential Read” refers to all other read database accesses, in which there may be more than one line returned. It is true that the term “Sequential read” is a little deceptive since it implies that blocks are always read sequentially (as in a full table scan).

What is buffer busy waits in Oracle?

The buffer busy wait event happens when a session tries to access a block in the buffer cache but it can’t because the buffer is busy, because another session is modifying the block and the contents of the block are in flux. Another session holds the buffer in an incompatible mode to our request.

What is db time in AWR report?

DB Time is the total time spent by the all user processes which are actively working or actively waiting in the database calls. It includes the CPU Time, IO Wait time and non-idle time.

What is db sequential read in Oracle 11g?

DB file sequential read (%) This event shows a wait for a foreground process while doing a sequential read from the database. The I/O is generally issued as a single I/O request to the OS; the wait blocks until the I/O request completes.

What do Db_file_sequential_read and db file scattered read event define?

A db file scattered read issues a scattered 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. The db file scattered read wait event identifies that a full scan is occurring.

What is control file what type of information it contains?

A control file is a small binary file that records the physical structure of the database and includes: The database name. Names and locations of associated datafiles and online redo log files. The timestamp of the database creation.

What is direct read?

direct-reading in British English adjective. (of an instrument) calibrated so that a given quantity to be measured can be read directly off the scale without the need of a multiplying constant.

How do you fix buffer busy waits?

The main way to reduce buffer busy waits is to reduce the total I/O on the system. This can be done by tuning the SQL to access rows with fewer block reads (i.e., by adding indexes). Even if we have a huge db_cache_size, we may still see buffer busy waits, and increasing the buffer size won’t help.