Datastores represent storage locations for virtual machine files. A storage location can be a VMFS volume, a directory on Network Attached Storage, or a local file system path. Datastores are platform-independent and host-independent.
Snapshot files are consuming a lot of datastore space.
The datastore is at full capacity when the used space is equal to the capacity. Allocated space can be larger than datastore capacity, for example, when you have snapshots and thin-provisioned disks.
Consider consolidating snapshots to the virtual disk when they are no longer needed. Consolidating the snapshots deletes the redo log files and removes the snapshots from the vSphere Web Client user interface.
You can provision more space to the datastore if possible, or you can add disks to the datastore or use shared datastores.