Notable changes

Deprecation of fetch-params.sh

The fetch-params.sh script (also zcash-fetch-params) is now deprecated. The zcashd binary now bundles zk-SNARK parameters directly and so parameters do not need to be downloaded or stored separately. The script will now do nothing but state that it is deprecated; it will be removed in a future release.

Previously, parameters were stored by default in these locations:

• ~/.zcash-params (on Linux); or
• ~/Library/Application Support/ZcashParams (on Mac); or
• C:\Users\Username\AppData\Roaming\ZcashParams (on Windows)

Unless you need to generate transactions using the deprecated Sprout shielded pool, you can delete the parameter files stored in these directories to save space as they are no longer read or used by zcashd. If you do wish to use the Sprout pool, you will need the sprout-groth16.params file in the aforementioned directory. This file is currently available for download here.

Mempool metrics

zcashd now reports the following new metrics when -prometheusport is set:

• (gauge) zcash.mempool.actions.unpaid { "bk" = ["< 0.2", "< 0.4", "< 0.6", "< 0.8", "< 1"] }
• (gauge) zcash.mempool.actions.paid
• (gauge) zcash.mempool.size.weighted { "bk" = ["< 1", "1", "> 1", "> 2", "> 3"] }

The zcash.mempool.actions metrics count the number of logical actions across the transactions in the mempool, while zcash.mempool.size.weighted is a weight-bucketed version of the zcash.mempool.size.bytes metric.

The ZIP 317 weight ratio of a transaction is used to bucket its logical actions and byte size. A weight ratio of at least 1 means that the transaction's fee is at least the ZIP 317 conventional fee, and all of its logical actions are considered "paid". A weight ratio lower than 1 corresponds to the fraction of the transaction's logical actions that are "paid". The remaining fraction (i.e. 1 - weight ratio) are subject to the unpaid action limit that miners configure for their blocks with -blockunpaidactionlimit.