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Overview

The set_account_data_writable syscall marks an account’s data as writable by the current executing program. This grants the program permission to modify the account’s data and metadata.

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Syscall Code

Code: 0x02 (TN_SYSCALL_CODE_SET_ACCOUNT_DATA_WRITABLE)

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C SDK Function

ulong tsys_set_account_data_writable(ulong account_idx);

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Arguments

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account_idx
ulong
required
Index of the account to mark as writable. Must be a valid account index within the transaction.

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Return Value

Returns a syscall result code:
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Success
ulong
  • TN_VM_SYSCALL_SUCCESS (0) - Account successfully marked as writable
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Error Codes
ulong
  • TN_VM_ERR_SYSCALL_INVALID_ACCOUNT_INDEX (-7) - Account index out of bounds
  • TN_VM_ERR_SYSCALL_ACCOUNT_NOT_WRITABLE (-26) - Account not writable in transaction or ownership check failed
  • TN_VM_ERR_SYSCALL_ACCOUNT_DOES_NOT_EXIST (-8) - Account does not exist

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Resource Consumption

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Compute Units

  • Base cost: TN_VM_SYSCALL_BASE_COST (512 units)
  • Additional cost: None
  • Total cost: Fixed at 512 units regardless of account state

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Memory Pages

  • Page usage: No direct page allocation or deallocation
  • Metadata impact: May trigger metadata page allocation if account metadata becomes writable

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Side Effects

  • Account state: Marks the account as writable by the current program
  • Write permissions: Grants the program ability to modify account data

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Usage Notes

  • The account must be marked as writable in the transaction (signer approval)
  • The account must be owned by the current program
  • Program accounts cannot be made writable
  • If the account is already writable by the current program, the syscall succeeds immediately
  • Once writable, the program can modify account data and metadata

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Ownership Rules

The account can be made writable only if:
  • The account is not a program account
  • The account is owned by the current executing program

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Example

#include "tn_sdk_syscall.h"

// Mark account at index 1 as writable
ulong account_idx = 1;
ulong result = tsys_set_account_data_writable(account_idx);

if (result == TN_VM_SYSCALL_SUCCESS) {
    // Account is now writable by this program
    // Can now modify account data and metadata
}