MongoDB’s cache is not configurable. Actually MongoDb uses all the free spaces on the system automatically by way of memory mapped files.
In MongoDB, there isn’t a direct method to configure a cache size in the same way you might configure a cache size for some other databases. MongoDB relies on the operating system’s virtual memory manager for most of its caching needs.
However, you can influence MongoDB’s cache behavior indirectly by adjusting the system’s virtual memory settings. The key file in MongoDB is the mongod process. You can limit its memory usage by configuring the system’s virtual memory settings.
For example, on Linux, you can use the ulimit command to set the virtual memory limits for the mongod process. The following command limits the virtual memory size to 2 gigabytes:
ulimit -v 2000000
Additionally, MongoDB has a configuration parameter called storage.wiredTiger.engineConfig.cacheSizeGB that you can set in the MongoDB configuration file. This parameter allows you to specify the maximum size of the WiredTiger cache in gigabytes. Here’s an example of how you can set it:
storage:
wiredTiger:
engineConfig:
cacheSizeGB: 2
Adjust the value of cacheSizeGB based on your available system memory and the specific requirements of your MongoDB deployment.
Remember to restart the MongoDB process after making changes to the configuration file for the changes to take effect.
It’s essential to note that MongoDB is designed to automatically manage its own caching based on the available system resources. Directly setting a cache size is often not necessary, and MongoDB generally performs well with its default settings. Adjusting cache sizes might be necessary only in specific scenarios and should be done carefully based on your system’s specifications and workload characteristics.