# SCCP-55: Change Debt Snapshot Stale Time to 12 Hours

Author Anton Jurisevic Implemented Governance Ethereum TBD TBD 2020-11-02

## Simple Summary

This SCCP proposes changing the debt snapshot stale time to 12 hours.

## Abstract

Following on from SCCP-52, the pDAO will call SystemSettings.setDebtSnapshotStaleTime(43800). Note that the argument corresponds to 12 hours and 10 minutes, allows the keeper bot 10 minutes of leeway to mine transactions while maintaining a 12 hour snapshot frequency. The keeper bot will still take snapshots earlier than 12 hours if the deviation exceeds its configured threshold of 1%, so lowering the frequency should not unduly impact the integrity of the system.

## Motivation

Snapshots have been operating reliably for several weeks with a stale time of 4 hours. In this period the system's debt deviation has not exceeded 1%. The debt snapshot deviation over the last two weeks is described in the following chart:

The dashed lines indicate the times at which complete snapshots were performed to prevent the snapshot going stale. The upper and lower bounds of this chart are the limits the deviation would have to breach in order to trigger a fresh snapshot.

The maximum deviation over this period was 0.76%. Most dramatic deviations in this period were corrected rapidly (and well before the next heartbeat) by exchange snapshot updates (see the relevant section of SIP-83) and market price corrections. As a result, there has still been no deviation-triggered partial snapshot over the time debt snapshots have been operating.

Most of the rationale for slowing down snapshots laid out in SCCP-52 still applies. We have learnt that synth exchange snapshot updates are effective, but have not seen its full benefit; and all the other reasons to slow the heartbeat still apply. We could still save significant resources by slowing the heartbeat and lowering the partial snapshot deviation threshold. A 12 hour snapshot frequency will still be well within the 24-hour issuance delay described in SIP-40, while further saving resources relative to the current 4 hour frequency. A final adjustment to a 24-hour snapshot heartbeat may happen in the future; but a twice-daily heartbeat should be a comfortable setting for some time to come.

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