Unlike most blockchain, Solana separates logic and data into two separate components: Program and Account. What that means is that instead of storing data inside variables internally, Programs interact with external data stored in Accounts with the ability to mutate them.
Account model
There are 3 kinds of accounts:
- Data accounts store data (which we use the most).
- System owned accounts.
- PDA(Program Derived Address) accounts.
- Program accounts store executable programs.
- Native accounts that indicate native programs on Solana such as System, Stake and Vote.
Each account has an address (usually a public key) and an owner (address of a program account). The full field list an account stores is found below.
| Field | Description |
|---|---|
| lamports | The number of lamports owned by this account |
| owner | The program owner of this account |
| executable | Whether this account can process instructions |
| data | The raw data byte array stored by this account |
| rent_epoch | The next epoch that this account will owe rent |
Ownership rules
There are a few important ownership rules:
- Only a data account's owner can modify its data and debit lamports.
- Anymore is allowed to credit lamports to a data account.
- The owner of an account may assign a new owner if the account's data is zeroed out.
Technically, the Programs are special kinds of Accounts marked as executable whose entire purpose is to store the compiled code of Program. The program accounts do not store state.
For example, if you create a counter program that lets you increment a counter, you must create two accounts, one account (account A) to store the program's code (executable = true), and one (account B) to store the counter value and account A must be the owner of account B.
Rent
- Storing data on accounts costs SOL to maintain, and it is funded by what is called
rent. - An account is considered rent-exempt if it holds at least 2 years worth of rent. Currently, all new accounts are required to be rent-exempt.
- Use the
getMinimumBalanceForRentExemptionRPC endpoint to calculate the minimum balance for a particular account size. - If the account does not have enough to pay rent, the account will be deallocated and the data removed.
