Connect a local parachain

In this tutorial, you'll connect a parachain to a local relay chain.

Tutorial objectives

By completing this tutorial, you will accomplish the following objectives:

  • Register a ParaID for your parachain on a relay chain.
  • Start block production of a parachain on a relay chain.

Before you begin

Before you begin, verify the following:

Build the parachain template

This tutorial uses the Substrate parachain template to launch a parachain on your local relay chain. The parachain template is similar to the node template used in solo chain development, so it should be quite familiar. Later, you'll use this parachain template as the starting point for developing your own parachains.

In a new terminal window:

# Clone the parachain template with the correct Polkadot version
git clone --depth 1 --branch polkadot-v0.9.26 https://github.com/substrate-developer-hub/substrate-parachain-template

# Switch into the parachain template directory
cd substrate-parachain-template

# Build the parachain template collator
cargo b -r

Compiling the node can take 15 to 60 minuets. In the mean time, reserve a ParaID on the running relay chain to prepare, and make not of the ParaID you acquire.

Reserve a ParaID

To connect to any relay chain, you must first reserve a ParaID for your parachain. It is called a ParaID because the same identifier can be used as a parachain ID or a parathread ID, depending on your current relay chain slot state. You must have a sufficient funds to reserve a ParaID. Refer to your target relay chain to determine the number of tokens required.

The relay chain is responsible for allotting all ParaIDs and simply increments starting at 2000 for all chains that are not common good parachains. These chains use a different method to allocate ParaIDs.

This exercise illustrates how to reserve a ParaID using Polkadot-JS Apps connecting to your local relay chain. Under the Network > Parachains sub-page, click on Parathreads tab and use the + ParaId button.

Reserve a `ParaID`

Note that the account used to reserve the ParaID must also be the origin for using this ParaID. After you submit this transaction and see a successful registrar.Reserved event with your paraID), you can launch your parachain or parathread using the reserved ID. You are now ready to generate the files required for your parachain using the reserved ParaID (ParaID 2000).

Custom parachain specification

Your chain specification must set the correct reserved ParaID for your parachain.

See the how-to guide on configuring a custom chain spec for more in-depth instructions to generate a plain spec, modify it, and generate a raw spec.

We first generate a plain spec with:

# Assumes that `rococo-local` is in `node/chan_spec.rs` as the relay you registered with
./target/release/parachain-collator build-spec --disable-default-bootnode > rococo-local-parachain-plain.json

Default ParaID is 1000 from Cumulus, so you must correctly set it for your parachain based on the reserved ParaID from above. Assuming your reserved ParaID is 2000, you will open rococo-local-parachain-plain.json and modify two fields:

  // --snip--
  "para_id": 2000, // <--- your already registered ID
  // --snip--
      "parachainInfo": {
        "parachainId": 2000 // <--- your already registered ID
      },
  // --snip--

Then generate a raw chain spec derived from your modified plain chain spec:

./target/release/parachain-collator build-spec --chain rococo-local-parachain-plain.json --raw --disable-default-bootnode > rococo-local-parachain-2000-raw.json

Save and distribute your raw spec

You must have a sufficient funds to reserve a ParaID. Refer to your target relay chain to determine the number of tokens required.

The relay chain is responsible for allotting all ParaIDs and simply increments starting at 2000 for all chains that are not common good parachains. These chains use a different method to allocate ParaIDs.

This exercise illustrates how to reserve a ParaID using Polkadot-JS Apps connecting to your local relay chain. Under the Network > Parachains sub-page, click on Parathreads tab and use the + ParaId button.

Reserve a `ParaID`

Note that the account used to reserve the ParaID must also be the origin for using this ParaID. After you submit this transaction and see a successful registrar.Reserved event with your paraID), you can launch your parachain or parathread using the reserved ID.

Obtain Wasm runtime validation function

The relay chain also needs the parachain-specific runtime validation logic to validate parachain blocks. The parachain collator node also has a command to produce this Wasm blob:

./target/release/parachain-collator export-genesis-wasm --chain rococo-local-parachain-2000-raw.json > para-2000-wasm

Generate a parachain genesis state

To register a parachain, the relay chain needs to know the parachain's genesis state. The collator node can export that state to a file. Go to your Parachain Template folder, the following command will create a file containing the parachain's entire genesis state, hex-encoded:

./target/release/parachain-collator export-genesis-state --chain rococo-local-parachain-2000-raw.json > para-2000-genesis

No pre-genesis blocks allowed

This runtime and state is for the parachain's genesis block only. You can't connect a parachain with any previous state to a relay chain. All parachains must start from block 0 on the relay chain. Eventually, migrating the block history of a solo chain built on Substrate is expected to be possible, but this functionality is not planned anytime soon.

See the guide on converting a solo chain to a parachain for details on how the parachain template was created and how to convert your chain's logic—not its history or state migrations—to a parachain.

Start a collator node

We can now start a single collator node. Notice that we need to supply the same relay chain chain spec we used for launching relay chain nodes at the second half of the command. Start a collator with the following command:

./target/release/parachain-collator \
--alice \
--collator \
--force-authoring \
--chain rococo-local-parachain-2000-raw.json \
--base-path /tmp/parachain/alice \
--port 40333 \
--ws-port 8844 \
-- \
--execution wasm \
--chain <relay chain raw chain spec> \
--port 30343 \
--ws-port 9977

The first thing to notice about this command is that several arguments are passed before the lone --, and several more arguments passed after it. A parachain collator contains the actual collator node and also an embedded relay chain node. The arguments before the -- are for the collator, and the arguments after the -- are for the embedded relay chain node.

We give the collator a base path and ports as we did for the relay chain node previously.

Remember to change the collator-specific values if you are executing these instructions a second time for a second parachain. You must use the same relay chain specification file, but different ParaID, base path, and port numbers for the second parachain collator to bind to.

There is presently no way to run a parachain node without the embedded relay chain node, but it is expected that this will become possible for non-collator nodes eventually.

At this point your collator's logs should look something like this:

2021-05-30 16:57:39 Parachain Collator Template
2021-05-30 16:57:39 ✌️  version 3.0.0-acce183-x86_64-linux-gnu
2021-05-30 16:57:39 ❤️  by Anonymous, 2017-2021
2021-05-30 16:57:39 📋 Chain specification: Local Testnet
2021-05-30 16:57:39 🏷 Node name: Alice
2021-05-30 16:57:39 👤 Role: AUTHORITY
2021-05-30 16:57:39 💾 Database: RocksDb at /tmp/parachain/alice/chains/local_testnet/db
2021-05-30 16:57:39 ⛓  Native runtime: template-parachain-1 (template-parachain-0.tx1.au1)
2021-05-30 16:57:41 Parachain id: Id(2000)
2021-05-30 16:57:41 Parachain Account: 5Ec4AhPUwPeyTFyuhGuBbD224mY85LKLMSqSSo33JYWCazU4
2021-05-30 16:57:41 Parachain genesis state: 0x0000000000000000000000000000000000000000000000000000000000000000000a96f42b5cb798190e5f679bb16970905087a9a9fc612fb5ca6b982b85783c0d03170a2e7597b7b7e3d84c05391d139a62b157e78786d8c082f29dcf4c11131400
2021-05-30 16:57:41 Is collating: yes
2021-05-30 16:57:41 [Parachain] 🔨 Initializing Genesis block/state (state: 0x0a96…3c0d, header-hash: 0xd42b…f271)
2021-05-30 16:57:41 [Parachain] ⏱  Loaded block-time = 12s from block 0xd42bb78354bc21770e3f0930ed45c7377558d2d8e81ca4d457e573128aabf271
2021-05-30 16:57:43 [Relaychain] 🔨 Initializing Genesis block/state (state: 0xace1…1b62, header-hash: 0xfa68…cf58)
2021-05-30 16:57:43 [Relaychain] 👴 Loading GRANDPA authority set from genesis on what appears to be first startup.
2021-05-30 16:57:44 [Relaychain] ⏱  Loaded block-time = 6s from block 0xfa68f5abd2a80394b87c9bd07e0f4eee781b8c696d0a22c8e5ba38ae10e1cf58
2021-05-30 16:57:44 [Relaychain] 👶 Creating empty BABE epoch changes on what appears to be first startup.
2021-05-30 16:57:44 [Relaychain] 🏷 Local node identity is: 12D3KooWBjYK2W4dsBfsrFA9tZCStb5ogPb6STQqi2AK9awXfXyG
2021-05-30 16:57:44 [Relaychain] 📦 Highest known block at #0
2021-05-30 16:57:44 [Relaychain] 〽️ Prometheus server started at 127.0.0.1:9616
2021-05-30 16:57:44 [Relaychain] Listening for new connections on 127.0.0.1:9945.
2021-05-30 16:57:44 [Parachain] Using default protocol ID "sup" because none is configured in the chain specs
2021-05-30 16:57:44 [Parachain] 🏷 Local node identity is: 12D3KooWADBSC58of6ng2M29YTDkmWCGehHoUZhsy9LGkHgYscBw
2021-05-30 16:57:44 [Parachain] 📦 Highest known block at #0
2021-05-30 16:57:44 [Parachain] Unable to listen on 127.0.0.1:9945
2021-05-30 16:57:44 [Parachain] Unable to bind RPC server to 127.0.0.1:9945. Trying random port.
2021-05-30 16:57:44 [Parachain] Listening for new connections on 127.0.0.1:45141.
2021-05-30 16:57:45 [Relaychain] 🔍 Discovered new external address for our node: /ip4/192.168.42.204/tcp/30334/ws/p2p/12D3KooWBjYK2W4dsBfsrFA9tZCStb5ogPb6STQqi2AK9awXfXyG
2021-05-30 16:57:45 [Parachain] 🔍 Discovered new external address for our node: /ip4/192.168.42.204/tcp/30333/p2p/12D3KooWADBSC58of6ng2M29YTDkmWCGehHoUZhsy9LGkHgYscBw
2021-05-30 16:57:48 [Relaychain] ✨ Imported #8 (0xe60b…9b0a)
2021-05-30 16:57:49 [Relaychain] 💤 Idle (2 peers), best: #8 (0xe60b…9b0a), finalized #5 (0x1e6f…567c), ⬇ 4.5kiB/s ⬆ 2.2kiB/s
2021-05-30 16:57:49 [Parachain] 💤 Idle (0 peers), best: #0 (0xd42b…f271), finalized #0 (0xd42b…f271), ⬇ 2.0kiB/s ⬆ 1.7kiB/s
2021-05-30 16:57:54 [Relaychain] ✨ Imported #9 (0x1af9…c9be)
2021-05-30 16:57:54 [Relaychain] ✨ Imported #9 (0x6ed8…fdf6)
2021-05-30 16:57:54 [Relaychain] 💤 Idle (2 peers), best: #9 (0x1af9…c9be), finalized #6 (0x3319…69a2), ⬇ 1.8kiB/s ⬆ 0.5kiB/s
2021-05-30 16:57:54 [Parachain] 💤 Idle (0 peers), best: #0 (0xd42b…f271), finalized #0 (0xd42b…f271), ⬇ 0.2kiB/s ⬆ 0.2kiB/s
2021-05-30 16:57:59 [Relaychain] 💤 Idle (2 peers), best: #9 (0x1af9…c9be), finalized #7 (0x5b50…1e5b), ⬇ 0.6kiB/s ⬆ 0.4kiB/s
2021-05-30 16:57:59 [Parachain] 💤 Idle (0 peers), best: #0 (0xd42b…f271), finalized #0 (0xd42b…f271), ⬇ 0 ⬆ 0
2021-05-30 16:58:00 [Relaychain] ✨ Imported #10 (0xc9c9…1ca3)

You should see your collator node running as a standalone node and its relay node connecting as a peer with the already running relay chain validator nodes.

Note if you do not see the embedded relay chain peering with local relay chain node, try disabling your firewall or adding the bootnodes parameter with the relay node's address.

It has not started authoring parachain blocks yet. Authoring will begin when the collator is actually registered on the relay chain.

Parachain Registration

There are a few methods possible to register a parachain to a relay chain. For testing, use of sudo is most common.

Register Using sudo

We have our relay chain launched and our parachain collator ready to go. Now we have to register the parachain on the relay chain. In a production network, this will typically be accomplished through parachain auctions. But for this tutorial we will do it with sudo call.

Registration Transaction

The transaction can be submitted on a relay chain node via Polkadot-JS Apps UI. There are multiple options to go about this, and we can pick any one of the following. Note that all options here depend on a paraID being reserved - so be sure to do that first.

If you are running a network with more than two validators you can add more parachains through the same interface with the parameters adjusted accordingly.

Option 1: paraSudoWrapper.sudoScheduleParaInitialize

This option bypasses the slot lease mechanics entirely to onboard a parachain or parathread for a reserved paraID starting on the next relay chain session. This is the simplest and fastest way to go about testing. These required files to register a parachain include details set in your chain specifications that must explicitly target the correct relay chain and use the right ParaID - in this case, rococo (instead of rococo-local used in this tutorial).

  • Go to Polkadot Apps UI, connecting to your relay chain.
  • Execute a sudo extrinsic on the relay chain by going to Developer -> sudo page.
  • Pick paraSudoWrapper -> sudoScheduleParaInitialize(id, genesis) as the extrinsic type, shown below.
parachain-registration-sudo.png
  • In the extrinsics parameters, specify:

    • Set the id: ParaId to 2,000
    • genesisHead: upload the file para-2000-genesis (from the previous step)
    • validationCode: upload the file para-2000-wasm (from the previous step)
    • Set the parachain: Bool option to Yes

This dispatch, if successful, will emit the sudo.Sudid event, viewable in the relay chain explorer page.

Option 2: slots.forceLease

This is the more formal flow for registration used in production (with the exception of the use of sudo to force a slot lease): you register your reserved paraID with the same account that reserved it, or use sudo with a registrar.forceRegister extrinsic if you wish.

Here we will use sudo to grant ourselves a lease. You should have an onboarded parathread:

parathread-onboarding.png
  • Go to Polkadot Apps UI, connecting to your relay chain.
  • Execute a sudo extrinsic on the relay chain by going to Developer -> sudo page.
  • Pick slots->forceLease(para, leaser, amount, period_begin, period_end) as the extrinsic type, shown below.
forceLease.png

Be sure to set the begin period to the slot you wish to start at. In testing, this is very likely to be the already active slot 0 if you started a fresh new relay chain. Extending this out to beyond the time you wish to test this parachain is likely the best, unless you want to test the onboarding and offboarding cycles. In that case, then electing slot leases that have gaps for a paraID would be in order. Once fully onboarded and after block production starts you should see:

parachain-active-lease.png

Block production

The collator should start producing parachain blocks (aka collating) once the registration is successful and the next relay chain epoch begin!

This may take a while! Be patient as you wait for the next epoch to start. This is 10 blocks for the example rococo-custom-2-raw.json included in the Prepare a local parachain testnet tutorial.

Finally, the collator should start producing log messages like the following:

# Notice the relay epoch change! Only then do we start parachain collating!
#
2021-05-30 17:00:04 [Relaychain] 💤 Idle (2 peers), best: #30 (0xfc02…2a2a), finalized #28 (0x10ff…6539), ⬇ 1.0kiB/s ⬆ 0.3kiB/s
2021-05-30 17:00:04 [Parachain] 💤 Idle (0 peers), best: #0 (0xd42b…f271), finalized #0 (0xd42b…f271), ⬇ 0 ⬆ 0
2021-05-30 17:00:06 [Relaychain] 👶 New epoch 3 launching at block 0x68bc…0605 (block slot 270402601 >= start slot 270402601).
2021-05-30 17:00:06 [Relaychain] 👶 Next epoch starts at slot 270402611
2021-05-30 17:00:06 [Relaychain] ✨ Imported #31 (0x68bc…0605)
2021-05-30 17:00:06 [Parachain] Starting collation. relay_parent=0x68bcc93d24a31a2c89800a56c7a2b275fe9ca7bd63f829b64588ae0d99280605 at=0xd42bb78354bc21770e3f0930ed45c7377558d2d8e81ca4d457e573128aabf271
2021-05-30 17:00:06 [Parachain] 🙌 Starting consensus session on top of parent 0xd42bb78354bc21770e3f0930ed45c7377558d2d8e81ca4d457e573128aabf271
2021-05-30 17:00:06 [Parachain] 🎁 Prepared block for proposing at 1 [hash: 0xf6507812bf60bf53af1311f775aac03869be870df6b0406b2969784d0935cb92; parent_hash: 0xd42b…f271; extrinsics (2): [0x1bf5…1d76, 0x7c9b…4e23]]
2021-05-30 17:00:06 [Parachain] 🔖 Pre-sealed block for proposal at 1. Hash now 0x80fc151d7ccf228b802525022b6de257e42388ec7dc3c1dd7de491313650ccae, previously 0xf6507812bf60bf53af1311f775aac03869be870df6b0406b2969784d0935cb92.
2021-05-30 17:00:06 [Parachain] ✨ Imported #1 (0x80fc…ccae)
2021-05-30 17:00:06 [Parachain] Produced proof-of-validity candidate. block_hash=0x80fc151d7ccf228b802525022b6de257e42388ec7dc3c1dd7de491313650ccae
2021-05-30 17:00:09 [Relaychain] 💤 Idle (2 peers), best: #31 (0x68bc…0605), finalized #29 (0xa6fa…9e16), ⬇ 1.2kiB/s ⬆ 129.9kiB/s
2021-05-30 17:00:09 [Parachain] 💤 Idle (0 peers), best: #0 (0xd42b…f271), finalized #0 (0xd42b…f271), ⬇ 0 ⬆ 0
2021-05-30 17:00:12 [Relaychain] ✨ Imported #32 (0x5e92…ba30)
2021-05-30 17:00:12 [Relaychain] Moving approval window from session 0..=2 to 0..=3
2021-05-30 17:00:12 [Relaychain] ✨ Imported #32 (0x8144…74eb)
2021-05-30 17:00:14 [Relaychain] 💤 Idle (2 peers), best: #32 (0x5e92…ba30), finalized #29 (0xa6fa…9e16), ⬇ 1.4kiB/s ⬆ 0.2kiB/s
2021-05-30 17:00:14 [Parachain] 💤 Idle (0 peers), best: #0 (0xd42b…f271), finalized #0 (0xd42b…f271), ⬇ 0 ⬆ 0
2021-05-30 17:00:18 [Relaychain] ✨ Imported #33 (0x8c30…9ccd)
2021-05-30 17:00:18 [Parachain] Starting collation. relay_parent=0x8c30ce9e6e9867824eb2aff40148ac1ed64cf464f51c5f2574013b44b20f9ccd at=0x80fc151d7ccf228b802525022b6de257e42388ec7dc3c1dd7de491313650ccae
2021-05-30 17:00:19 [Relaychain] 💤 Idle (2 peers), best: #33 (0x8c30…9ccd), finalized #30 (0xfc02…2a2a), ⬇ 0.7kiB/s ⬆ 0.4kiB/s
2021-05-30 17:00:19 [Parachain] 💤 Idle (0 peers), best: #1 (0x80fc…ccae), finalized #0 (0xd42b…f271), ⬇ 0 ⬆ 0
2021-05-30 17:00:22 [Relaychain] 👴 Applying authority set change scheduled at block #31
2021-05-30 17:00:22 [Relaychain] 👴 Applying GRANDPA set change to new set [(Public(88dc3417d5058ec4b4503e0c12ea1a0a89be200fe98922423d4334014fa6b0ee (5FA9nQDV...)), 1), (Public(d17c2d7823ebf260fd138f2d7e27d114c0145d968b5ff5006125f2414fadae69 (5GoNkf6W...)), 1)]
2021-05-30 17:00:22 [Relaychain] 👴 Imported justification for block #31 that triggers command Changing authorities, signaling voter.
2021-05-30 17:00:24 [Relaychain] ✨ Imported #34 (0x211b…febf)
2021-05-30 17:00:24 [Parachain] Starting collation. relay_parent=0x211b3c53bebeff8af05e8f283d59fe171b7f91a5bf9c4669d88943f5a42bfebf at=0x80fc151d7ccf228b802525022b6de257e42388ec7dc3c1dd7de491313650ccae
2021-05-30 17:00:24 [Parachain] 🙌 Starting consensus session on top of parent 0x80fc151d7ccf228b802525022b6de257e42388ec7dc3c1dd7de491313650ccae
2021-05-30 17:00:24 [Parachain] 🎁 Prepared block for proposing at 2 [hash: 0x10fcb3180e966729c842d1b0c4d8d2c4028cfa8bef02b909af5ef787e6a6a694; parent_hash: 0x80fc…ccae; extrinsics (2): [0x4a6c…1fc6, 0x6b84…7cea]]
2021-05-30 17:00:24 [Parachain] 🔖 Pre-sealed block for proposal at 2. Hash now 0x5087fd06b1b73d90cfc3ad175df8495b378fffbb02fea212cc9e49a00fd8b5a0, previously 0x10fcb3180e966729c842d1b0c4d8d2c4028cfa8bef02b909af5ef787e6a6a694.
2021-05-30 17:00:24 [Parachain] ✨ Imported #2 (0x5087…b5a0)
2021-05-30 17:00:24 [Parachain] Produced proof-of-validity candidate. block_hash=0x5087fd06b1b73d90cfc3ad175df8495b378fffbb02fea212cc9e49a00fd8b5a0
2021-05-30 17:00:24 [Relaychain] 💤 Idle (2 peers), best: #34 (0x211b…febf), finalized #31 (0x68bc…0605), ⬇ 1.0kiB/s ⬆ 130.1kiB/s
2021-05-30 17:00:24 [Parachain] 💤 Idle (0 peers), best: #1 (0x80fc…ccae), finalized #0 (0xd42b…f271), ⬇ 0 ⬆ 0
2021-05-30 17:00:29 [Relaychain] 💤 Idle (2 peers), best: #34 (0x211b…febf), finalized #32 (0x5e92…ba30), ⬇ 0.2kiB/s ⬆ 0.1kiB/s
2021-05-30 17:00:29 [Parachain] 💤 Idle (0 peers), best: #1 (0x80fc…ccae), finalized #0 (0xd42b…f271), ⬇ 0 ⬆ 0
2021-05-30 17:00:30 [Relaychain] ✨ Imported #35 (0xee07…38a0)
2021-05-30 17:00:34 [Relaychain] 💤 Idle (2 peers), best: #35 (0xee07…38a0), finalized #33 (0x8c30…9ccd), ⬇ 0.9kiB/s ⬆ 0.3kiB/s
2021-05-30 17:00:34 [Parachain] 💤 Idle (0 peers), best: #1 (0x80fc…ccae), finalized #1 (0x80fc…ccae), ⬇ 0 ⬆ 0
2021-05-30 17:00:36 [Relaychain] ✨ Imported #36 (0xe8ce…4af6)
2021-05-30 17:00:36 [Parachain] Starting collation. relay_parent=0xe8cec8015c0c7bf508bf3f2f82b1696e9cca078e814b0f6671f0b0d5dfe84af6 at=0x5087fd06b1b73d90cfc3ad175df8495b378fffbb02fea212cc9e49a00fd8b5a0
2021-05-30 17:00:39 [Relaychain] 💤 Idle (2 peers), best: #36 (0xe8ce…4af6), finalized #33 (0x8c30…9ccd), ⬇ 0.6kiB/s ⬆ 0.1kiB/s
2021-05-30 17:00:39 [Parachain] 💤 Idle (0 peers), best: #2 (0x5087…b5a0), finalized #1 (0x80fc…ccae), ⬇ 0 ⬆ 0

Block finalization

The relay chain tracks the latest block (the head) of each parachain. When a relay chain block is finalized, every parachain blocks that have completed the validation process are also finalized. This is how Polkadot achieves pooled, shared security for it's parachains!

You can see the registered parachains and their latest data by clicking Network > Parachains in the Apps UI.

parachain-summary-screenshot.png

Interact with your parachain

The entire point of launching and registering parachains is that we can submit transactions to the parachains and interact with them. We are finally ready to submit extrinsics on our parachains!

Connecting with the Apps UI

We've already connected the Apps UI to the relay chain node. Now we can also connect to the parachain collator. Open another instance of Apps UI in a new browser window, and connect it to the appropriate endpoint. If you have followed this tutorial so far, you can connect to the parachain node at:

https://polkadot.js.org/apps/?rpc=ws%3A%2F%2Flocalhost%3A8844#/

Submit extrinsics

You can make some simple token transfers to ensure that the parachain is operating normally. You can also make some on-chain remarks by going to the Extrinsics page, choosing System pallet and remark extrinsic.

If the transaction go through as expected, you have a working parachain.

Congratulations!

Read on for more optional material.

Cross-chain Message Passing (XCMP)

The defining feature of connecting parachains to a common relay chain is the ability to communicate between all connected chains. This area of functionality is at the cutting edge development and is not included in this tutorial.

To learn more about XCMP, refer to Polkadot wiki on XCMP.

Chain purging

Your sole collator is the only home of the parachain blockchain data as there is only one node on your entire parachain network. Relay chains only store parachains header information. If the parachain data is lost, you will not be able to recover the chain. In testing though, you may need to start things from scratch.

To purge your parachain chain data from the relay chain, you need to deregister and re-register the parachain collator. It may be easier in testing to instead just purge the relay and parachains and start again form genesis. You can purge all chain data for all chains by running the following commands:

# Purge the collator(s)
./target/release/parachain-collator purge-chain \
  --base-path <your collator DB path set above>

# Purge the validator(s)
polkadot purge-chain \
  --base-path <your relay chain DB path set above>

Then register from a blank slate again.

Next steps