How to modify Oracle database memory

As a highly large database system, Oracle database requires relatively high hardware resources for its operation, including system memory. The running speed and performance of a database system largely depend on the size and configuration of memory. If there is insufficient memory or unreasonable configuration, it will affect the performance of the Oracle database system, causing problems such as slow response and frequent crashes in the system. Therefore, adjusting the memory configuration of the Oracle database is one of the key measures to ensure system performance. This article will briefly introduce how to modify Oracle database memory.

1. Memory structure

In the Oracle database system, the memory structure includes SGA and PGA. SGA (System Global Area) refers to the shared memory area used by Oracle database during execution, including Buffer Cache, Shared Pool, Large Pool, Java Pool, etc. SGA stores a large amount of data from the database on the physical disk. When a user requests access to this database, the data will be loaded into SGA to improve access speed. PGA (Process Global Area) refers to the private memory area used by each process in the Oracle database system, including Sort Area, Hash Join Area, etc. PGA stores process-level metadata information, variables, caches, and processing results, etc., and is mainly used to store temporary data during SQL execution.

2. Modify SGA memory

If you want to modify the SGA memory of the Oracle database system, you need to perform the following steps:

(1) Determine the available physical memory

First you need to determine the available physical memory. This can be determined by looking at the operating system's memory usage. If there are other applications running on the system, you need to consider the memory resources occupied by these programs.

(2) Calculate SGA memory allocation

Calculate SGA memory allocation according to the actual situation. It is best to use Oracle's own SGA automatic adjustment function. If you use manual configuration, you need to determine the memory size of each component based on the actual situation. You need to be careful not to allocate all memory to the Buffer Cache, because other components also have a great impact on the performance of the system. If there is enough memory, it is recommended to allocate more memory to Shared Pool and Library Cache.

(3) Modify the init.ora configuration file

Before modifying the SGA memory of the Oracle database system, you need to modify the init.ora configuration file as needed to ensure that the modified memory configuration can be System identification. Parameters such as sga_max_size, sga_target and pga_aggregate_target can be found in the configuration file and modified as needed.

(4) Start the database

After completing the above steps, you need to restart the Oracle database system to make the new memory configuration take effect. At this time, you can use SQL statements to check whether the actual configuration of SGA is consistent with the previous modification.

3. Modify PGA memory

If you want to modify the PGA memory of the Oracle database system, you need to adjust the pga_aggregate_target parameter according to the actual situation. This parameter indicates the maximum limit of PGA memory that can be used by the Oracle database system. The value of this parameter can be increased or decreased according to requirements. It should be noted that modifying the PGA memory has a relatively small impact on the overall system performance, but it will have a more obvious impact on some large and complex query statements.

4. Best practices for adjusting memory size

(1) The memory capacity must be sufficient

Whether you are modifying SGA memory or PGA memory, You need to ensure that the memory capacity is sufficient, otherwise system bottlenecks will occur. If the computer running the Oracle database system does not have enough memory, you can increase the memory or limit the number of other programs running on the system.

(2) Make full use of the automatic adjustment function

The Oracle database system provides an automatic adjustment function, which can dynamically allocate memory according to the actual situation to avoid the problem of too large or too small memory.

(3) Pay attention to the maximum size of SGA

When modifying SGA memory, one parameter that needs to be paid attention to is sga_max_size. This parameter limits the maximum size of SGA. If it is set too small, SGA will be unable to accommodate more data; if it is set too large, system memory resources will be wasted.

(4) Balance the memory allocation of each component

When adjusting the SGA memory, balance the memory allocation of each component. Do not allocate all memory to the Buffer Cache. Other components also have a negative impact on the system. Performance has a big impact.

(5) Test the new memory configuration

After modifying the memory of the Oracle database system, testing is required to verify its effect, especially some complex SQL statements need to be tested to ensure performance Not affected.

In summary, modifying Oracle database memory is a task that needs to be handled with caution. Improper memory configuration will have a great impact on system performance. Therefore, before making modifications, you should understand the structure and function of the memory and make a reasonable ratio based on the actual situation. It is recommended to back up the database before modifying it to ensure data security.

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