Using Blobs

This guide walks you through how to switch to using blobs for your chain after Ecotone is activated.

This guide is intended for chains already upgraded to Ecotone.

Switch to using blobs

Determine scalar values for using blobs

The first step to switching to submit data with Blobs is to calculate the scalar values you wish to set for the formula to charge users fees. To determine the scalar values to use for your chain, you can utilize this fee parameter calculator (opens in a new tab) to get a better estimate for scalar values on your chain. Input the average transaction per day your chain is processing, the types of transactions that occur on your chain, the OP_BATCHER_MAX_CHANNEL_DURATION you have parameterized on your op-batcher, and the target margin you wish to charge users on top of your L1 costs. The following information is tuned to a network like OP Mainnet. For more details on fee scalar, see Transaction Fees, Ecotone section.

Adjust fees to change margins

As a chain operator, you may want to scale your scalar values up or down either because the throughput of your chain has changed and you are either filling significantly more or less of blobs, or because you wish to simply increase your margin to cover operational expenses. So, to increase or decrease your margin on L1 data costs, you would simply scale both the l1baseFeeScalar and the l1blobBaseFeeScalar by the same multiple.

For example, if you wished to increase your margin on L1 data costs by ~10%, you would do:

newBaseFeeScalar= prevBaseFeeScalar * 1.1
newBlobBaseFeeScalar = prevBlobBaseFeeScalar * 1.1

Update your scalar values for blobs

Once you have determined your ideal BaseFeeScalar and BlobBaseFeeScalar, you will need to apply those values for your chain. The first step is to encode both values into a single value to be set in your L1 Config:

You can set your Scalar Values to send transaction to the L1 SystemConfigProxy.setGasConfigEcotone

cast send \
--private-key $GS_ADMIN_PRIVATE_KEY \
--rpc-url $ETH_RPC_URL \
<CONTRACT_ADDRESS> \
"setGasConfigEcotone(uint32,uint32)" \
<basefeeScalar> <blobbasefeeScalar>

Check that the gas price oracle on L2 returns the expected values for baseFeeScalar and blobBaseFeeScalar (wait ~1 minute):

This is checked on L2, so ensure you are using an RPC URL for your chain. You'll also need to provide a gas-price to geth when making this call.

cast call 0x420000000000000000000000000000000000000F 'baseFeeScalar()(uint256)' --rpc-url YOUR_L2_RPC_URL

Update your batcher to post blobs

Now that the fee config has been updated, you should immediately configure your batcher!

⚠️

Your chain may be undercharging users during the time between updating the scalar values and updating the Batcher, so aim to do this immediately after.

Steps to configure the batcher:

Configure OP_BATCHER_DATA_AVAILABILITY_TYPE=blobs. The batcher will have to be restarted for it to take effect.
Ensure your OP_BATCHER_MAX_CHANNEL_DURATION is properly set to maximize your fee savings. See OP Batcher Max Channel Configuration for more details.
Optionally, you can configure your batcher to support multi-blobs. See Multi-Blob Batcher Configuration for more details.

Switch back to using calldata

As a chain operator, if the blobBaseFee is expensive enough and your chain is not processing enough transactions to meaningfully fill blobs within your configured batcher OP_BATCHER_MAX_CHANNEL_DURATION, you may wish to switch back to posting data to calldata. Utilize the fee parameter calculator (opens in a new tab) to inform whether your transactions will be cheaper if submitting blobs or if submitting calldata. Chains can follow these steps to switch from blobs back to using calldata.

Determine your scalar values for using calldata

If you are using calldata, then you can set your BaseFeeScalar similarly to how you would have set "scalar" prior to Ecotone, though with a 5-10% bump to compensate for the removal of the "overhead" component. You can utilize this fee parameter calculator (opens in a new tab) to get a better estimate for scalar values on your chain. The following information is tuned to a network like OP Mainnet.

Chains can update their fees to increase or decrease their margin. If using calldata, then BaseFeeScalar should be scaled to achieve the desired margin. For example, to increase your L1 Fee margin by 10%:

BaseFeeScalar = BaseFeeScalar * 1.1
BlobBaseFeeScalar = 0

Update your scalar values for using calldata

To set your scalar values, follow the same process as laid out in Update your Scalar values for Blobs.

Update your batcher to post calldata

Now that the fee config has been updated, you will want to immediately configure your batcher.

💡

Reminder, that your chain may be undercharging users during the time between updating the scalar values and updating the Batcher, so aim to do this immediately after.

Configure OP_BATCHER_DATA_AVAILABILITY_TYPE=calldata. The batcher will have to be restarted for it to take effect.
Ensure your OP_BATCHER_MAX_CHANNEL_DURATION is properly set to maximize savings. NOTE: While setting a high value here will lower costs, it will be less meaningful than for low throughput chains using blobs. See OP Batcher Max Channel Configuration for more details.

Other considerations

For information on L1 Data Fee changes related to the Ecotone upgrade, visit the Transaction Fees page.
If you want to enable archive nodes, you will need to access a blob archiver service. You can use Optimism's or run your own.