By default, ApsaraDB for MyBase allocates dedicated CPU and memory to each instance. If your workloads have low average CPU utilization, most of that capacity goes unused. Resource overcommitment lets you run more instances on each host by sharing physical resources, which improves CPU utilization and reduces infrastructure costs.
How overcommitment works
Without overcommitment, a 32-core, 256 GB host can run four 8-core, 64 GB instances, with resources fully isolated between them.
With a CPU Overcommit Ratio of 200%, the same host can run eight 8-core, 32 GB instances. Instances share physical CPU cycles, which is efficient when their peak usage periods don't overlap.
Background
In industries such as gaming, the user growth trends of new services are unpredictable. Purchasing a large number of ApsaraDB RDS instances ahead of time can lead to wasted resources. Resource overcommitment lets you run more instances on the same hosts while monitoring host performance:
If the number of users grows faster than expected, you can purchase additional hosts and migrate specific instances to the new hosts.
If the number of users grows slower than expected, you can configure resource overcommitment to meet business requirements and reduce resource costs.
Set overcommit ratios
After creating a dedicated cluster, configure overcommit ratios based on your host type and instance specifications.
Log on to the ApsaraDB for MyBase console.
On the Dedicated Clusters page, find the cluster, and then click Edit in the Actions column. The Edit Dedicated Cluster panel appears.
In the Edit Dedicated Cluster panel, configure the following parameters:
Parameter Description CPU Overcommit Ratio The ratio of allocated CPU resources to physical CPU resources for the cluster. At 200%, up to twice as many CPU cores can be allocated compared with the physical cores available. Storage Overcommit Ratio The ratio of allocated storage to physical storage for each host in the cluster. Maximum Memory Usage The maximum memory utilization allowed for each host in the cluster. Only configurable for ApsaraDB for MyBase for MySQL dedicated clusters. 
Click OK. To verify the configuration, find the cluster on the Dedicated Clusters page, click Details in the Actions column, and then view the settings on the Basic Information page.
What to do if host load increases
If host load increases after you enable overcommitment, add hosts to the cluster and migrate high-load instances to the new hosts:
To add hosts, see Create a host.
To move existing instances to the new hosts, see Migrate an instance to another host.