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# Algorand Specifications

* * *

| Parameter Name | Default Value | Introduced in Version | Last Updated in Version |
| --- | --- | --- | --- |
| `Archival` | `false` | 0 | 0 |

**Description:**

Enables saving a full copy of the blockchain history. Non-Archival nodes will only
maintain the necessary state to validate blockchain messages and participate in
the consensus protocol. Non-Archival nodes use significantly less storage space.

> The `Archival` parameter enables the node to save the complete history of the
> blockchain starting from the moment this setting is activated. Therefore, this
> setting must be enabled **before** you start the node for the first time. If the
> node has already been running without this setting enabled, the existing databases
> must be **deleted** and fully synchronized from the genesis.

* * *

| Parameter Name | Default Value | Introduced in Version | Last Updated in Version |
| --- | --- | --- | --- |
| `HotDataDir` | Empty string | 31 | 31 |

**Description:**

An optional directory to store data frequently accessed by the node. For isolation,
the node will create a subdirectory in this location, named by the network [`genesisID`](https://specs.algorand.co/ledger/ledger-genesis#genesis-identifier)
The node uses the default data directory provided at runtime if not specified. Individual
resources may override this setting. Setting `HotDataDir` to a dedicated high-performance
disk allows for basic disk tuning.

* * *

| Parameter Name | Default Value | Introduced in Version | Last Updated in Version |
| --- | --- | --- | --- |
| `ColdDataDir` | Empty string | 31 | 31 |

**Description:**

An optional directory for storing infrequently accessed data. The node creates a
subdirectory within this location, named after the network [`genesisID`](https://specs.algorand.co/ledger/ledger-genesis#genesis-identifier)
The node uses the default data directory provided at runtime if not specified. Individual
resources may have their own override settings, which take precedence over this value.
A slower disk for `ColdDataDir` can optimize storage costs and resource allocation.

* * *

| Parameter Name | Default Value | Introduced in Version | Last Updated in Version |
| --- | --- | --- | --- |
| `TrackerDBDir` | Empty string | 31 | 31 |

**Description:**

An optional directory to store the tracker database. For isolation, the node will
create a subdirectory in this location, named by the network [`genesisID`](https://specs.algorand.co/ledger/ledger-genesis#genesis-identifier).
If not specified, the node will use the `HotDataDir`.

* * *

| Parameter Name | Default Value | Introduced in Version | Last Updated in Version |
| --- | --- | --- | --- |
| `BlockDBDir` | Empty string | 31 | 31 |

**Description:**

An optional directory to store the [block](https://specs.algorand.co/ledger/ledger-block) database.
For isolation, the node will create a subdirectory in this location, named by the
network [`genesisID`](https://specs.algorand.co/ledger/ledger-genesis#genesis-identifier). If not specified,
the node will use the `ColdDataDir`.

* * *

| Parameter Name | Default Value | Introduced in Version | Last Updated in Version |
| --- | --- | --- | --- |
| `CatchpointDir` | Empty string | 31 | 31 |

**Description:**

An optional directory to store _Catchpoint Files_, except for the in-progress temporary
file, which will use the `HotDataDir` and is not separately configurable. For isolation,
the node will create a subdirectory in this location, named by the network [`genesisID`](https://specs.algorand.co/ledger/ledger-genesis#genesis-identifier).
If not specified, the node will use the `ColdDataDir`.

* * *

| Parameter Name | Default Value | Introduced in Version | Last Updated in Version |
| --- | --- | --- | --- |
| `StateproofDir` | Empty string | 31 | 31 |

**Description:**

An optional directory to persist state about observed and issued [state proof messages](https://specs.algorand.co/ledger/ledger-state-proofs#message).
For isolation, the node will create a subdirectory in this location, named by the
network [`genesisID`](https://specs.algorand.co/ledger/ledger-genesis#genesis-identifier). If not specified,
the node will use the `HotDataDir`.

* * *

| Parameter Name | Default Value | Introduced in Version | Last Updated in Version |
| --- | --- | --- | --- |
| `CrashDBDir` | Empty string | 31 | 31 |

**Description:**

An optional directory to persist [Agreement participation](https://specs.algorand.co/abft/abft)
state. For isolation, the node will create a subdirectory in this location, named
by the network [`genesisID`](https://specs.algorand.co/ledger/ledger-genesis#genesis-identifier). If
not specified, the node will use the `HotDataDir`

* * *

| Parameter Name | Default Value | Introduced in Version | Last Updated in Version |
| --- | --- | --- | --- |
| `OptimizeAccountsDatabaseOnStartup` | `false` | 10 | 10 |

**Description:**

Controls whether the Account database would be optimized on [`algod`](https://specs.algorand.co/node/non-normative/node-nn-algod)
startup.

* * *

| Parameter Name | Default Value | Introduced in Version | Last Updated in Version |
| --- | --- | --- | --- |
| `LedgerSynchronousMode` | `2` | 12 | 12 |

**Description:**

Defines the synchronous mode the [Ledger](https://specs.algorand.co/ledger/ledger-overview) database
uses.

The supported options are:

- `0`: SQLite continues without syncing as soon as it has handed data off to the operating system.
- `1`: SQLite database engine will still sync at the most critical moments, but less often than in FULL mode.
- `2`: SQLite database engine will use the VFS’s xSync method to ensure all content
is safely written to the disk surface before continuing.
- `3`: In addition to what is being done in `2`, it provides some guarantee of durability
if the commit is followed closely by a power loss.

> For further information, see the description of [`SynchronousMode`](https://github.com/algorand/go-algorand/blob/b6e5bcadf0ad3861d4805c51cbf3f695c38a93b7/util/db/dbutil.go#L435).

* * *

| Parameter Name | Default Value | Introduced in Version | Last Updated in Version |
| --- | --- | --- | --- |
| `AccountsRebuildSynchronousMode` | `1` | 12 | 12 |

**Description:**

Defines the synchronous mode the [Ledger](https://specs.algorand.co/ledger/ledger-overview) database uses while the Account database
is being rebuilt. This is not a typical operational use-case, and is expected to
happen only on either startup (after enabling the _Catchpoint Interval_, or on certain
database upgrades) or during fast catchup. The values specified here and their meanings
are identical to the ones in `LedgerSynchronousMode`.

* * *

| Parameter Name | Default Value | Introduced in Version | Last Updated in Version |
| --- | --- | --- | --- |
| `MaxAcctLookback` | `4` | 23 | 23 |

**Description:**

Sets the maximum lookback range for Account states.

> Important  
> **EXAMPLE:**  
> The Ledger can answer Account state questions for the range `[Latest - MaxAcctLookback, Latest]`.

* * *

| Parameter Name | Default Value | Introduced in Version | Last Updated in Version |
| --- | --- | --- | --- |
| `MaxBlockHistoryLookback` | `0` | 31 | 31 |

**Description:**

Sets the maximum lookback range for Block information.

> Important  
> **EXAMPLE:**  
> The Block DB can return transaction IDs for questions for the range `[Latest - MaxBlockHistoryLookback, Latest]`.

* * *

| Parameter Name | Default Value | Introduced in Version | Last Updated in Version |
| --- | --- | --- | --- |
| `StorageEngine` | `sqlite` | 28 | 28 |

**Description:**

Sets the type of storage to use for the Ledger. Available options are:

- `sqlite` (default).  
- `pebbledb` (experimental, in development).

* * *