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ENPT-BRES
Programming Model

Realloc (Account Resize)

The process of resizing an on-chain account's data allocation after creation. Realloc can increase or decrease the data field size, but each instruction can increase by at most 10,240 bytes (10KB). The account owner program must sign the realloc, and if the account grows, additional lamports must be provided to maintain rent exemption. In Anchor, the realloc constraint on #[account(mut, realloc = new_size, realloc::payer = payer, realloc::zero = false)] handles this automatically.

IDrealloc
Plain meaning

Plain meaning

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The process of resizing an on-chain account's data allocation after creation. Realloc can increase or decrease the data field size, but each instruction can increase by at most 10,240 bytes (10KB). The account owner program must sign the realloc, and if the account grows, additional lamports must be provided to maintain rent exemption. In Anchor, the realloc constraint on #[account(mut, realloc = new_size, realloc::payer = payer, realloc::zero = false)] handles this automatically.

Mental model

Mental model

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Think of it as one of the core moving pieces your program reads, writes, or invokes at runtime.

Technical context

Technical context

Place the term inside its Solana layer so the definition is easier to reason about.

Accounts, instructions, PDAs, transactions, and execution flow.

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Why builders care

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Realloc (Account Resize) (realloc)
Category: Programming Model
Definition: The process of resizing an on-chain account's data allocation after creation. Realloc can increase or decrease the data field size, but each instruction can increase by at most 10,240 bytes (10KB). The account owner program must sign the realloc, and if the account grows, additional lamports must be provided to maintain rent exemption. In Anchor, the realloc constraint on #[account(mut, realloc = new_size, realloc::payer = payer, realloc::zero = false)] handles this automatically.
Related: Account, Rent Exemption, Account Data
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Concept graph

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Branch

Account

The fundamental data storage unit on Solana. Every piece of state is stored in an account identified by a 32-byte public key. Accounts hold a lamport balance, an owner program, a data byte array (up to 10MB), and an executable flag. Only the owning program can modify an account's data, but anyone can credit lamports to it.

Public Key (Pubkey)Lamport
Open term
Branch

Rent Exemption

The state where an account holds enough lamports to cover two years of rent, making it effectively permanent. The minimum balance is approximately 0.00089088 SOL per byte of data. Since Solana requires all new accounts to be rent-exempt, this is the minimum funding required when creating accounts.

Rent
Open term
Branch

Account Data

The byte array stored in an account that holds program-specific state. Data is typically serialized using Borsh and must be explicitly allocated at account creation. The maximum data size is 10MB. Programs are responsible for defining and managing their own data layout, including discriminators for type identification.

Serialization / DeserializationBorsh
Open term
Next concepts to explore

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Programming Model

Account

The fundamental data storage unit on Solana. Every piece of state is stored in an account identified by a 32-byte public key. Accounts hold a lamport balance, an owner program, a data byte array (up to 10MB), and an executable flag. Only the owning program can modify an account's data, but anyone can credit lamports to it.

Open term
Programming Model

Rent Exemption

The state where an account holds enough lamports to cover two years of rent, making it effectively permanent. The minimum balance is approximately 0.00089088 SOL per byte of data. Since Solana requires all new accounts to be rent-exempt, this is the minimum funding required when creating accounts.

Open term
Programming Model

Account Data

The byte array stored in an account that holds program-specific state. Data is typically serialized using Borsh and must be explicitly allocated at account creation. The maximum data size is 10MB. Programs are responsible for defining and managing their own data layout, including discriminators for type identification.

Open term
Programming Model

Rent

A fee mechanism that charges accounts for storing data on-chain. Accounts must maintain a minimum lamport balance proportional to their data size (~6.96 SOL per MB) to be rent-exempt. Since 2022, all new accounts must be rent-exempt at creation. Accounts falling below the threshold are removed during rent collection.

Open term
Commonly confused with

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Programming Modelaccount

Account

The fundamental data storage unit on Solana. Every piece of state is stored in an account identified by a 32-byte public key. Accounts hold a lamport balance, an owner program, a data byte array (up to 10MB), and an executable flag. Only the owning program can modify an account's data, but anyone can credit lamports to it.

Open term
Programming Modelaccount-data

Account Data

The byte array stored in an account that holds program-specific state. Data is typically serialized using Borsh and must be explicitly allocated at account creation. The maximum data size is 10MB. Programs are responsible for defining and managing their own data layout, including discriminators for type identification.

Open term
Programming Modelbuffer-account

Buffer Account

A temporary account used during Solana program deployment to hold the program's ELF binary before it is written to the program data account. The deployer creates a buffer account, uploads the compiled SBF binary in chunks via the Upgradeable BPF Loader's Write instruction, and then issues a Deploy or Upgrade instruction that copies the buffer contents to the final program data account. Buffer accounts can be closed after deployment to reclaim rent.

Open term
Related terms

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Programming Modelaccount

Account

The fundamental data storage unit on Solana. Every piece of state is stored in an account identified by a 32-byte public key. Accounts hold a lamport balance, an owner program, a data byte array (up to 10MB), and an executable flag. Only the owning program can modify an account's data, but anyone can credit lamports to it.

Open term
Programming Modelrent-exemption

Rent Exemption

The state where an account holds enough lamports to cover two years of rent, making it effectively permanent. The minimum balance is approximately 0.00089088 SOL per byte of data. Since Solana requires all new accounts to be rent-exempt, this is the minimum funding required when creating accounts.

Open term
Programming Modelaccount-data

Account Data

The byte array stored in an account that holds program-specific state. Data is typically serialized using Borsh and must be explicitly allocated at account creation. The maximum data size is 10MB. Programs are responsible for defining and managing their own data layout, including discriminators for type identification.

Open term
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Programming Model

Account

The fundamental data storage unit on Solana. Every piece of state is stored in an account identified by a 32-byte public key. Accounts hold a lamport balance, an owner program, a data byte array (up to 10MB), and an executable flag. Only the owning program can modify an account's data, but anyone can credit lamports to it.

Open term
Programming Model

Program

Executable code deployed on-chain, equivalent to a smart contract on other blockchains. Programs are stateless—they store no data themselves but read/write data in separate accounts they own. Programs are compiled to SBF bytecode and loaded via the BPF Loader. Every program has a unique Program ID (its account's public key).

Open term
Programming Model

Instruction

A single operation within a transaction that invokes a program. An instruction specifies: (1) the program ID to call, (2) an array of account metas (pubkey, is_signer, is_writable), and (3) an opaque data byte array. Programs decode the instruction data to determine which operation to perform.

Open term
Programming Model

Transaction

An atomic unit of execution containing one or more instructions, a recent blockhash, and one or more signatures. All instructions in a transaction execute sequentially and atomically—if any instruction fails, the entire transaction reverts. Transactions have a 1,232-byte size limit (matching IPv6 MTU) and a default 200,000 CU budget.

Open term