# Data transaction

Data transaction is a transaction that writes data to an account data storage.

Each data transaction has a data array that contains data to be written. In JSON representation of a transaction the data array is the field data.

# Data array of a data transaction

The maximum length of an array is 100 elements.

The maximum size of an array is 150 kilobytes.

Each element of an array is an object that has 3 fields: key, type, value.

An array cannot contain two elements with the same key field.

# The `key` field

The key field is a non-empty UTF-8 string.

At the stage of transaction validation, the key field is converted from UTF-8 to UTF-16 encoding. The size of the resulting array of 16-bit words must not exceed 100 elements. Thus, the size of the key must be from 1 to 200 bytes inclusive.

The key is being deleted when its type and value are not specified.

This functionality becomes available since node version 1.2.0, after activation of feature #15 “Ride V4, VRF, Protobuf, Failed transactions”. Versions 1.2.x are currently available on Stagenet only.

When deleting a key using the JSON representation of a transaction, null is used as the type and value of the key. In one data transaction, keys can be used both for writing and deleting records. The maximum number of keys to be deleted in one transaction cannot exceed 100.

# The `type` field

The type field specifies the type of the value field:

binary
boolean
integer
string

# The `value` field

The size of value field can be from 0 to 32767 bytes.

# Binary format

See the page Data transaction binary format.

# Data transaction

# Data array of a data transaction

# The key field

# The type field

# The value field

# Binary format

# The `key` field

# The `type` field

# The `value` field