Ethereum Classic (ETC) blocks specify the maximum allowed gas in total that their transactions can use. I will discuss these maxima.

Basics

Block gas maxima are set by miners. Changes cannot be greater than or equal to a factor of 1 / 1024. For example, suppose the parent has a block gas maximum of 10,240. This implies the next block can only have values between 10,231 and 10,249 since:

10240 + 10240 // 1024 - 1 = 10249 10240 - 10240 // 1024 + 1 = 10231

The only exception is for values below that of the first block, or 5000, which are not allowed.

Block gas maxima are also the maxima for single transactions. A transaction using the maximum allowed gas needs to be the only transaction in its block.

Example

Block 7,275,504 has five transactions which together require 7,875,636 gas units. This is just under the block gas maximum of 7,875,709.

Debate

There are different opinions regarding the optimal block gas maxima. Some argue that smaller values lead to smaller blocks, less uncles and faster verifications. Small values, therefore, may increase security and decrease centralization. Others argue that larger values lead to greater mining rewards which may attract more miners. Therefore, some say larger values may also increase security and decrease centralization!

Conclusion

Block gas maxima limit transactions. These maxima are themselves limited in how quickly they can change. Their values affect the security and level of decentralization of ETC and hence must be chosen carefully.

Feedback

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Acknowledgements

I would like to thank IOHK (Input Output Hong Kong) for funding this effort.

License

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International License.