In move the global storage structure is a persistent storage area that allows developers to store data on the blockchain.
The global storage structure in MOVE consists of a mapping data type, which is similar to a hash table or dictionary in other programming languages. This mapping data type allows developers to store key-value pairs, where the key is a unique identifier and the value is the data to be stored.
The purpose of Move programs is to read from and write to tree-shaped persistent global storage. Programs cannot access the filesystem, network, or any other data outside of this tree.
In pseudocode, the global storage looks something like:
struct GlobalStorage {
resources: Map<(address, ResourceType), ResourceValue>
modules: Map<(address, ModuleName), ModuleBytecode>
}Structurally, global storage is a forest consisting of trees rooted at an account address. Each address can store both resource data values and module code values. As the pseudocode above indicates, each address can store at most one resource value of a given type and at most one module with a given name.