# Protocol Documentation
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## Table of Contents

- [storagegroup/types.proto](#storagegroup/types.proto)

  - Messages
    - [StorageGroup](#neo.fs.v2.storagegroup.StorageGroup)
    

- [Scalar Value Types](#scalar-value-types)



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## storagegroup/types.proto


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<a name="neo.fs.v2.storagegroup.StorageGroup"></a>

### Message StorageGroup
StorageGroup keeps verification information for Data Audit sessions. Objects
that require payed storage guaranties are gathered in `StorageGroups` with
additional information used for proof of storage. `StorageGroup` only
contains objects from the same container.

Being an object payload, StorageGroup may have expiration Epoch set with
`__NEOFS__EXPIRATION_EPOCH` well-known attribute. When expired, StorageGroup
will be ignored by InnerRing nodes during Data Audit cycles and will be
deleted by Storage Nodes.


| Field | Type | Label | Description |
| ----- | ---- | ----- | ----------- |
| validation_data_size | [uint64](#uint64) |  | Total size of the payloads of objects in the storage group |
| validation_hash | [neo.fs.v2.refs.Checksum](#neo.fs.v2.refs.Checksum) |  | Homomorphic hash from the concatenation of the payloads of the storage group members. The order of concatenation is the same as the order of the members in the `members` field. |
| expiration_epoch | [uint64](#uint64) |  | DEPRECATED. Last NeoFS epoch number of the storage group lifetime |
| members | [neo.fs.v2.refs.ObjectID](#neo.fs.v2.refs.ObjectID) | repeated | Strictly ordered list of storage group member objects |

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## Scalar Value Types

| .proto Type | Notes | C++ Type | Java Type | Python Type |
| ----------- | ----- | -------- | --------- | ----------- |
| <a name="double" /> double |  | double | double | float |
| <a name="float" /> float |  | float | float | float |
| <a name="int32" /> int32 | Uses variable-length encoding. Inefficient for encoding negative numbers – if your field is likely to have negative values, use sint32 instead. | int32 | int | int |
| <a name="int64" /> int64 | Uses variable-length encoding. Inefficient for encoding negative numbers – if your field is likely to have negative values, use sint64 instead. | int64 | long | int/long |
| <a name="uint32" /> uint32 | Uses variable-length encoding. | uint32 | int | int/long |
| <a name="uint64" /> uint64 | Uses variable-length encoding. | uint64 | long | int/long |
| <a name="sint32" /> sint32 | Uses variable-length encoding. Signed int value. These more efficiently encode negative numbers than regular int32s. | int32 | int | int |
| <a name="sint64" /> sint64 | Uses variable-length encoding. Signed int value. These more efficiently encode negative numbers than regular int64s. | int64 | long | int/long |
| <a name="fixed32" /> fixed32 | Always four bytes. More efficient than uint32 if values are often greater than 2^28. | uint32 | int | int |
| <a name="fixed64" /> fixed64 | Always eight bytes. More efficient than uint64 if values are often greater than 2^56. | uint64 | long | int/long |
| <a name="sfixed32" /> sfixed32 | Always four bytes. | int32 | int | int |
| <a name="sfixed64" /> sfixed64 | Always eight bytes. | int64 | long | int/long |
| <a name="bool" /> bool |  | bool | boolean | boolean |
| <a name="string" /> string | A string must always contain UTF-8 encoded or 7-bit ASCII text. | string | String | str/unicode |
| <a name="bytes" /> bytes | May contain any arbitrary sequence of bytes. | string | ByteString | str |