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Oracle database is currently the most widely used relational database management system in the world. In the Oracle database server, the memory setting has a great impact on its performance. Therefore, when setting the Oracle database memory, we need to make careful and detailed adjustments in order to achieve the best operating results.
In the Oracle database architecture, the memory mainly includes two parts: System Global Area (SGA) and Process Global Area (PGA). SGA is shared memory, used to store all core objects such as data dictionaries, shared pools, and data caches; while PGA is an independent memory space for each process, used to store session-private variables and data.
When configuring Oracle memory, you need to follow the following principles:
2.1 Be aware of the adverse effects of insufficient memory
Insufficient memory configuration of Oracle database will cause performance degradation, increase IO operations for data reading, and even cause database downtime and other problems.
2.2 Consider database load
Before configuring memory, you need to understand the database load, including the number of concurrent connections, concurrent access, data volume, etc., in order to allocate memory to SGA and PGA and Make appropriate adjustments.
2.3 Maintain system stability
While adjusting memory, system stability must be ensured. When setting memory, you need to consider factors such as the server's memory size and the number of CPUs to avoid problems such as insufficient system memory and excessive CPU utilization.
When configuring Oracle database memory, you need to go through the following steps:
3.1 Understand the system memory
Before configuring memory, you first need to understand the memory status of the server to determine the size available for memory allocation. You can use the command "free -m" to check the memory size.
3.2 Set the size of SGA
The size of SGA is very important in the Oracle database. It stores most of the data and objects in the Oracle database. SGA usually includes data cache, shared pool, redo log cache, etc. You can use the following command to calculate the size of SGA.
SGA_MAX_SIZE = max(Shared Pool Buffer Cache Other Pools), SGA_TARGET = min(Shared Pool Buffer Cache Other Pools);
Among them, Shared Pool refers to the shared pool size, and Buffer Cache refers to is the data cache size, and Other Pools refers to the size of other pools. Things like area size (Block Size), cache latency, etc. should all be taken into consideration.
3.3 Set the size of PGA
The size setting of PGA is related to memory allocation and process. The maximum memory space of a process is controlled by PGA_AGGREGATE_TARGET. The default value usually used is 2GB, but it can be adjusted to a more reasonable value.
3.4 Adjust memory configuration
Once the sizes of SGA and PGA are determined, corresponding memory configuration adjustments are also required when adjusting the Oracle database. This can be adjusted using the command ALTER SYSTEM.
In the memory settings of Oracle database, many factors need to be considered and need to be adjusted according to the actual situation. Both SGA and PGA are very important components and need to be adjusted separately when adjusting the memory. At the same time, when setting up memory, you need to pay attention to the stability of the database system and the load of the database to achieve the best operating results.
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