Recommended Value for setting the ORACLE database server SWAP to, oracleswap

Recommended Value for setting the ORACLE database server SWAP to, oracleswap
1. Role of swap

Both system management and DBA know that there is a SWAP partition on both Linux and UNIX systems, which is similar to the virtual memory on Windows systems.

When the system's physical memory is insufficient, you need to release some of the physical memory space and temporarily transfer it to the SWAP to provide the physical memory space for the currently running program, when the program needs to access the data transferred to the SWAP space, it will recover the data from the SWAP to the physical memory. Since then, it is hard to see how SWAP works. If SWAP is used, it is not recommended to use it. If it is used, memory switching will occur, which will inevitably affect the system performance.

2. swap settings

Experienced system administrators and DBAs often construct a SWAP with a moderate size for the system. However, in actual production systems, it is often found that SWAP is too small, the physical memory and SWAP are all exhausted, resulting in a DOWN-to-machine situation. It is also found that the necessary storage space is wasted because the SWAP settings are too large, and the size of the SWAP settings is large, refer to the official ORACLE suggestions.

3. ORACLE officially recommends setting standards for swap

For the operating system running the ORACLE database, ORACLE officially recommends setting the size. Here we take the recommended size extracted from the ORACLE 12C R1 official document as an example:

4.3.4 Server Memory Minimum Requirements Ensure that your system meets the following memory requirements: Minimum: 1 GB of RAM Recommended: 2 GB of RAM or more Table 4-3 describes the relationship between the installed RAM and the configured swap space recommendation: Table 4-3 Swap Space Requirement for Linux RAM Swap Space Between 1 GB and 2 GB 1.5 times the size of the RAM Between 2 GB and 16 GB Equal to the size of the RAM More than 16 GB 16 GB

(1) ORACLE officially requires a minimum RAM of 1 GB. 2 GB or larger is recommended.

(2) Relationship between SWAP and RAM size Configuration

1) When RAM is 1-2 GB, it is recommended that the SWAP size be 1.5 times the RAM size.

2) When RAM is 2-16 GB, we recommend that the SWAP size be equal to the RAM size.

3) When RAM is greater than 16 GB, the recommended SWAP size is 16 GB.

4. Recommended SWAP size configuration in a large memory Environment

Due to the rapid decline in memory prices, it is not surprising that the current production system servers have 256 GB of memory and GB of physical memory. In the case of 16-64 GB physical memory, SWAP and physical memory are "equivalent, when the memory size is larger than 64 GB, we recommend that you set it to half or equal to the physical memory size. The specific size can be determined based on experience. You can adjust the SWAP size when you continuously observe SWAP usage during the production process.

 

 

Author: LI Junjie (Network Name: Step-by-Step), engaged in "system architecture, operating system, storage device, database, middleware, application" six levels of systematic performance optimization work

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