Oracle is one of the most popular relational database management systems in the world, and it is widely used in enterprise-level applications. However, when using Oracle, it is critical to make reasonable memory settings based on actual conditions. This article will introduce the basics of Oracle memory settings and some useful tips.
In Oracle database, RAM (random access memory) is a very important resource, which affects the performance and performance of the entire database system. stability. The main purpose of memory settings is to improve the performance and reliability of the database system by optimizing RAM usage.
According to Oracle's design standards, the entire RAM will be allocated to multiple key components, such as SGA (system global area), PGA (program global area), shared pool (shared pool), buffer cache (buffer cache) and Java pool (Java pool).
In Oracle, there are some important parameters that control the way memory is used. The following are some of the most important parameters:
a. SGA_TARGET
This parameter controls the size of SGA. SGA is the most used memory area by Oracle and is used to store directories, table spaces, and data blocks. Important information such as buffers and shared pools. When setting this parameter, you need to consider the total amount of system memory and the settings of other parameters.
b. PGA_AGGREGATE_TARGET
This parameter is used to control the size of PGA. PGA is used to store process-level data and information, mainly including sorting, aggregation and hash operations. If the size of the PGA is too small, the performance of query operations may decrease; if the size of the PGA is too large, system memory may be exhausted and other system resources may be affected.
c. SHARED_POOL_SIZE
This parameter is used to control the size of the shared pool. The shared pool stores the SQL parse tree, execution plan, and various metadata information. Generally, if this parameter is set too small, it will lead to insufficient shared pool, thus affecting the execution of SQL.
d. DB_CACHE_SIZE
This parameter is used to set the size of the buffer cache. This area is used to cache data block information to improve read performance. If the area is set too small, it will cause the system to frequently read disk data, thereby affecting performance; if it is set too large, it will occupy too much system memory.
When setting memory parameters, it should be evaluated based on the system hardware and actual application load conditions. The following are some common tips and suggestions:
a. Configure SGA_TARGET equivalent to physical memory
In order to fully utilize the system memory, SGA_TARGET needs to be set to be equal to or close to the physical memory size of the system. It is generally recommended to set aside 20% of space for kernel cache use.
b. Allocate 1/3 of the available memory to PGA, and allocate the rest to SGA
Too little memory will cause PGA and SGA to compete for space, affecting system performance. It is recommended to allocate 1/3 of the available memory to PGA and the rest to SGA.
c. Avoid fragmentation of the buffer pool
When using Oracle, due to the architecture of the buffer pool, the buffer block is easily divided into small segments. Therefore, memory settings need to reserve a certain amount of space to avoid fragmentation, which in turn affects system performance.
d. Consider the speed of the hard disk when setting the memory size
Generally, if the system uses a slow disk as the storage medium, the overall size of the memory needs to be limited to 1-2GB; if the system If you use a fast hard drive, consider using a larger memory cache.
Oracle memory setting is a very important topic, it has a decisive impact on the performance and stability of the database system. Understanding and implementing correct memory settings requires operations personnel to have a solid technical background and practical experience. This article briefly introduces the basic knowledge of Oracle memory settings and some practical tips. I hope it will be helpful to readers.
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