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
