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.