oracle memory modification

Oracle memory modification

Oracle is the current leader in enterprise-level database systems. Despite this, some users always encounter some memory limit issues. Oracle can either use shared memory or files in the operating system's file system, but either way, memory limitations may affect Oracle's performance, and we will need to make some adjustments and memory modifications for this issue.

Why is there a memory limit?

Oracle will pre-allocate a piece of memory as the main storage area when it starts, so the initial amount of memory for the program is determined. During operation, Oracle may automatically increase memory, such as the size of automatic shared memory, but you need to carefully check whether the memory size exceeds the physical memory size limit. If the limit is exceeded, the operating system will forcefully terminate Oracle execution.

How to adjust shared memory?

Shared memory is implemented at the operating system level. The operating system reserves a memory block as shared memory and grants Oracle user permissions to use the memory block. In order to adjust the shared memory, we can follow the steps below:

1. View the size of the shared memory in the system

Check the manual of the operating system and Oracle version you are using to find out How to view allocated shared memory. Taking Linux as an example, use the "ipcs -m" command to check the size of the shared memory.

2. Change the shared memory size

Many parameters of the operating system can be adjusted while maintaining at least one of the same extreme values ​​in the minimum list of each process. On the Oracle system side, there are two parameters that can be used to change the size of shared memory: SGA and PGA.

• SGA (System Global Area), used to allocate Oracle's memory in shared memory. This can be tuned using Oracle's SGA utility.
• PGA (Program Global Area) is used to allocate a certain amount of memory to each process. You can set PGA_LIMIT in the startup options to change the size, or you can use PGA_AGGREGATE_TARGET to let Oracle adjust the size automatically.

You need to modify these parameters carefully to avoid affecting the overall stability of the system.

How to adjust the file memory in the operating system file system?

File memory in the operating system file system also affects Oracle performance. They are called Shared Memory Files and are usually created by the operating system to store shared memory. The following are some common files:

• /dev/shm: A temporary file system used to create shared memory files under Linux.
• /tmp: Used to store shared memory files in many Linux installations.
• /var/tmp: Another directory used to store shared memory files.

Before adjusting the memory file size, you need to determine the currently used file directory and obtain permissions. You can use the following command to view the currently used directory and its size:

df -h /dev/shm

Next, you can try to adjust some parameters of using the directory, such as inode, Quantity and size. You can modify these parameters using the mount command, or change the parameters of the operating system itself. If you're not sure how to adjust these parameters, check your operating system's official documentation.

Conclusion

Oracle is a very powerful enterprise-level database system. Despite this, some users still experience some memory limit issues. We can help Oracle overcome these limitations by tuning shared memory and file memory in the operating system file system. However, before making any changes, be sure to consult the official documentation in order to properly understand and modify the parameters of the database and operating system.

The above is the detailed content of oracle memory modification. For more information, please follow other related articles on the PHP Chinese website!