<p>this means "init database engine. load data from disk to memory"</p>

CC BY-SA 3.0
2017-01-27T14:19:56.133Z
ok, and after that it verifies the blocks, is still a local job or does the verifying already connects with the internet/network?
mvanderbilt
CC BY-SA 3.0
2017-01-27T14:41:01.213Z
verifying blocks in database is local job.
amaclin
CC BY-SA 3.0
2017-01-27T14:17:55.877Z
2017-01-27T14:17:55.877Z
amaclin
<blockquote>
  <p>When I start up my Bitcoin core, it says "loading block index".</p>
</blockquote>

<p>The Bitcoin Core node software maintains several pieces of data on disk (excluding the wallet):</p>

<ul>
<li>The actual blocks in append-only data files.</li>
<li>The block index (which block headers exist, how they interconnect, and where on disk they are stored)</li>
<li>The chain state (the set of unspent outputs with amount, txid and address) at the current best block in the index.</li>
</ul>

<p>Because this information about what blocks are known and where they are on disk is so frequently needed, it is loaded entirely into memory.</p>

<p>During the "loading block index", the full block index is loaded into memory (it's pretty small, 60 MB at the time of writing), and several consistency checks are done (including verifying all difficulties and proof of work).</p>

<blockquote>
  <p>Does this indexing occur on my local machine</p>
</blockquote>

<p>Yes.</p>

<blockquote>
  <p>or does this mean my wallet fetches the latest block info, more specifically the block height?</p>
</blockquote>

<p>No, fetching information about new blocks always occurs in the background while your node is active, but during the "Loading block index" phase it is not yet active.</p>

<blockquote>
  <p>What is the purpose of this block indexing?</p>
</blockquote>

<p>By index you perhaps are thinking of something more fancy than it is. It's simply a table that allows you to look a block's information based on its hash.</p>

<p>Bitcoin Core internally has dozens of indexes for various pieces of data. This is just one that is relatively big, and stored on disk.</p>

CC BY-SA 3.0
2017-01-28T16:51:25.843Z
2017-01-28T16:51:25.843Z
Pieter Wuille
<p>When I start up my Bitcoin core, it says "loading block index". Does this indexing occur on my local machine or does this mean my wallet fetches the latest block info, more specifically the block height?
What is the purpose of this block indexing?
Thanks</p>

<bitcoin-core>
Block index versus Block height
mvanderbilt
# Block index versus Block height

(Asked by: username_0 on 2017-01-27)

When I start up my Bitcoin core, it says "loading block index". Does this indexing occur on my local machine or does this mean my wallet fetches the latest block info, more specifically the block height?
What is the purpose of this block indexing?
Thanks

**Tags:** bitcoin-core


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## 2 answers

### Answer by username_2 on 2017-01-28. Score: 5 | Accepted answer

> When I start up my Bitcoin core, it says "loading block index".

The Bitcoin Core node software maintains several pieces of data on disk (excluding the wallet):

* The actual blocks in append-only data files.
* The block index (which block headers exist, how they interconnect, and where on disk they are stored)
* The chain state (the set of unspent outputs with amount, txid and address) at the current best block in the index.

Because this information about what blocks are known and where they are on disk is so frequently needed, it is loaded entirely into memory.

During the "loading block index", the full block index is loaded into memory (it's pretty small, 60 MB at the time of writing), and several consistency checks are done (including verifying all difficulties and proof of work).

> Does this indexing occur on my local machine

Yes.

> or does this mean my wallet fetches the latest block info, more specifically the block height?

No, fetching information about new blocks always occurs in the background while your node is active, but during the "Loading block index" phase it is not yet active.

> What is the purpose of this block indexing?

By index you perhaps are thinking of something more fancy than it is. It's simply a table that allows you to look a block's information based on its hash.

Bitcoin Core internally has dozens of indexes for various pieces of data. This is just one that is relatively big, and stored on disk.


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### Answer by username_1 on 2017-01-27. Score: 1

this means "init database engine. load data from disk to memory"

> **Comments:**
> **username_0**: ok, and after that it verifies the blocks, is still a local job or does the verifying already connects with the internet/network?  
> **username_1**: verifying blocks in database is local job.  

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