# Import Database

### Nodes can revalidate an existing database by importing it and initializing with designated flags.

#### Blockchain State Verification and Data Indexing

Checking the blockchain state at a specific point in time, ensuring software compatibility, validating blockchain integrity, and indexing data from genesis to the present are critical tasks for maintaining a secure and efficient blockchain system. This guide covers how to:

* **Check Blockchain State at a Specific Time**: This involves using APIs or direct database access to examine the state of the blockchain at a given block number (e.g., block 255255). For example, one could import the database module and configure the node to pause at the block of interest.
* **Ensure Backwards Compatibility with New Software Versions**: It's crucial to verify that updates or new versions of the blockchain software do not introduce compatibility issues with existing data and functionalities.
* **Validate Blockchain State**: Regularly validating the integrity and consistency of the blockchain state helps in identifying and rectifying discrepancies early.
* **Index Data in Elasticsearch**: For enhanced query capabilities and analytics, you can index all the blockchain data, from the genesis block to the latest, into a search engine like Elasticsearch.

### How to start the process[​](https://docs.multiversx.com/validators/import-db#how-to-start-the-process) <a href="#how-to-start-the-process" id="how-to-start-the-process"></a>

Let's suppose we have the following data structure:

```
  ~/of-chain-go/cmd/node
```

The `node` binary is in the specified path. We also have a database built from a continuously syncing observer with the chain from genesis without shard switching.. This database will be placed in a directory, let's presume we will place it near the node's binary, yielding a data structure as follows:

```
.
├── config
│    ├── api.toml
│    ├── config.toml
│    ...
├── import-db
│    └── db
│        └── 1
│            ├── Epoch_0
│            │     └── Shard_1
│            │         ├── BlockHeaders
│            │         │   ...
│            │         ├── BootstrapData
│            │         │   ...
│            │         ...
│            └── Static
│                  └── Shard_1
│                      ...
├── node
```

Ensure the `db` directory is a subdirectory of `import-db`. Verify that the `config` directory, especially the `prefs.toml` file, matches the original node's configuration.

{% hint style="danger" %}
WARNING

Before you begin the import-db process, ensure that the `/of-chain-go/cmd/node/db` directory is completely empty. This will allow the import to start from the genesis block and proceed up to the last available epoch.
{% endhint %}

Next, the node can be started by using:

```
 cd ~/of-chain-go/cmd/node
 ./node -use-log-view -log-level *:INFO -import-db ./import-db
```

{% hint style="info" %}
NOTE

The `-import-db` flag designates the path to the source database directory. In the given example, it's assumed the directory is named `import-db` and is situated close to the `node` executable.
{% endhint %}

The node will start the reprocessing of the provided database. It will end with a message like:

```
import ended because data from epochs [x] or [y] does not exist
```

{% hint style="info" %}
NOTE

To accelerate the import-db process, omit checking block header signatures when using data from a trusted source. Add the `-import-db-no-sig-check` flag upon starting the node, alongside previously mentioned flags.
{% endhint %}

### Import-DB with populating an Elasticsearch cluster[​](https://docs.multiversx.com/validators/import-db#import-db-with-populating-an-elasticsearch-cluster) <a href="#import-db-with-populating-an-elasticsearch-cluster" id="import-db-with-populating-an-elasticsearch-cluster"></a>

Utilizing the `import-db` mechanism allows for the efficient population of an Elasticsearch cluster by re-processing data through this process.

{% hint style="info" %}
NOTE

Import-DB for populating an Elasticsearch cluster should be used only for a full setup (a node in each Shard + a Metachain node)
{% endhint %}

* To prepare, update the `external.toml` file on each node.&#x20;
* Use Import-DB only for full setups. &#x20;
* Nodes will push re-processed data to the Elasticsearch cluster if configured correctly.

{% hint style="warning" %}
**More details will be released when the testnet phase starts.**
{% endhint %}


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