Oracle 参数 LOG_BUFFER 官方解释,作用,如何配置最优化建议

本站中文解释

LOG_BUFFER参数控制了Redo Log缓冲器的大小,即redo log buffer的大小,默认情况下,当redo block大小为512 bytes时,该值为4MB,当redo block大小为2KB时,该值为16MB,当redo block大小为4KB时,该值为32MB。该参数的值可以设置为任意值,但是不应该太大,一般不超过128MB,因为太大会占用很多内存空间,影响Oracle数据库性能。必须要保证多个redo log buffer 之和应该小于”log_checkpoint_interval”参数值。

另外,要正确设置LOG_BUFFER参数,需要考虑的因素有:
1. 数据库的负载情况;
2. 数据库的活动时间和空闲时间比例;
3. 是否使用并发性;
4. 数据库服务器的内存容量,尤其是对I/O相关参数所关联的内存容量。

根据以上因素,可以根据数据库的实际情况,视redo block大小而灵活调整LOG_BUFFER参数的值,以确保数据库的正常运行。

官方英文解释

LOG_BUFFER specifies the amount of memory (in bytes) that Oracle uses when buffering redo entries to a redo log file.

Property Description

Parameter type

Big integer

Default value

2 MB to 32 MB, depending on the SGA size and CPU count

Modifiable

No

Modifiable in a PDB

No

Range of values

2 MB to operating system-dependent

Basic

No

Redo log entries contain a record of the changes that have been made to the database block buffers. The LGWR process writes redo log entries from the log buffer to a redo log file.

The log buffer size depends on the number of redo strands in the system. One redo strand is allocated for every 16 CPUs and has a default size of 2 MB. Oracle allocates a minimum of 2 redo strands per instance. When the log buffer size is not specified, any remaining memory in the redo granules is given to the log buffer.

See Also:

  • Your operating system-specific Oracle documentation for the default value and range of values

  • Oracle Database
    Performance Tuning Guide
    for information on resizing the redo log buffer using this parameter


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