Oracle background processes and large pool____oracle

The large pool is used to allocate large memory to handle the larger memory of the shared pool and is a standby pool to ease Oracle's pressure on shared pool and PGA memory use

The main objects used with large pool are:

Multithreaded Server MTS: Allocating UGA in the large_pool of the SGA

Parallel query Parallel exection for statements: used as a message buffer between processes

Recovery Manager Rman: Used as a disk IO buffer at backup

To view the default setting value of the Large_pool parameter, 0 should indicate that the ASMM is turned on

Show Parameter Large_pool_size

View ASMM actual allocation size during Large_pool current run

Select Pool,sum (bytes) from V$sgastat group by pool;

Java Pool

Oracle has added Java support to the kernel, which is designed for Java development and application, and it is not necessary to change the default size of the buffer without Java programs

To view the default setting value of the Java_pool parameter, 0 should indicate that the ASMM is turned on

Show Parameter Java_pool_size

View ASMM actual allocation size during Java_pool current run

Select Pool,sum (bytes) from V$sgastat group by pool;

Streams_buffer

Buffering for Convection replication

View Size

Show parameter streams_pool_size;

Redo_log_buffer

Any modifications to the database are recorded sequentially in the buffer, and then the LGWR process writes to the Redolog file on the disk in batches based on conditional change information to conserve disk IO, which does not participate in ASMM dynamic management and is not automatically resized

View Redo_log_buffer Size

Show parameter Log_buffer;

Select Name,bytes from V$sgastat where name= ' Log_buffer ';

Manually modify Redo_log_buffer Size

Alter system set log_buffer=6000000 Scope=spfile;

Oracle Process:

Background process

Server process

User process

Background process:

A background process is an Oracle program that manages the reading, writing, recovery, and monitoring of a database, primarily through background processes and user processes, and by data exchange between background processes and user processes

To view a background process that is already running

$ps-ef |grep Ora_

Sql>select name,description from v$bgprocess where paddr!= ' 00 ';

DBWN (Database write process)

Data buffer data is written to the data file, is responsible for data buffer management of a background process. The default number is 1, up to 10.

Data buffer Fast write disk, you want to write each data cache fast content to the data file in the specified fast, because these designations are usually discontinuous, so write these fast is called discrete write, because the head needs to repeatedly locate the data file within the specified fast, and the head repeated positioning is time-consuming, so the discrete write is relatively slow

The role of DBWN:

The LRU algorithm manages the data buffer, writes the modified dirty buffer data to the data file, maintains clean of the data buffer so that the user process can always find enough free buffers

Optimizes disk IO reading and writing by delaying write data

Lgwr

Writes log data from the log buffer to the Redolog log file group, where the contents of each log buffer block are written to a specified speed and are written to each fast in the log file, so they are called sequential writes and are faster in sequential writes.

The role of LGWR ·:

Manage • Log buffers, write database changes to log files to maintain data consistency and provide a basis for recovery after data loss

Optimizing Disk IO reading and writing by delaying write logging

About transactions

' One transaction generates one or more redo records, and a redo record contains multiple change vectors, which, when restored with log data, take the smallest unit