set_oldest_stored_round

Call v301 → current #2

Sets the oldest round number that the chain will retain in storage .

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Used by: validatorsdevelopers

The Big Picture

Storing every Drand pulse forever would consume unbounded storage. This call sets a floor - pulses below this round may be pruned or considered unavailable. It's a storage management tool that balances historical data availability against chain state size.

Why This Matters

If your application needs historical randomness, you need to know the availability window. This call defines that window. Pulses older than OldestStoredRound may not be queryable.

Example Scenario

Chain has been running for a year with millions of stored pulses. Governance decides to keep only the last month's worth. They calculate the oldest round for 30 days ago and call set_oldest_stored_round(that_round). Applications querying older rounds get defaults.

Common Questions

Does this immediately delete old pulses?
The semantic is 'oldest retained' - actual deletion may be lazy or triggered separately. The storage item marks intent; cleanup may follow.
How do I know what rounds are available?
Query OldestStoredRound and LastStoredRound to get the available range. Rounds outside this range return empty/default values.

Use Cases

  • Manage storage costs by limiting historical pulse retention
  • Set data retention policy for randomness history
  • Coordinate with pruning or archival strategies

From Chain Metadata

allows the root user to set the oldest stored round

Part of: Distributed Randomness

Input Parameters

#NameTypeDescription
0
oldest_round
u64 oldest_round (u64)

Permissions

Origin
Unknown
Required Role
Any

Permission data inferred from metadata. May be incomplete.

Requirements

  • Caller has root/sudo privileges
  • New oldest round is valid (not greater than LastStoredRound)

Effects

Events Emitted

SetOldestStoredRound

Storage Modified

OldestStoredRound

Postconditions

  • OldestStoredRound storage updated
  • SetOldestStoredRound event emitted

Side Effects

  • Pulses below this round may be pruned or become inaccessible
  • Reduces storage requirements for historical randomness

Code Examples

import { ApiPromise, WsProvider } from "@polkadot/api";
import { stringCamelCase } from "@polkadot/util";

const provider = new WsProvider("wss://entrypoint-finney.opentensor.ai:443");
const api = await ApiPromise.create({ provider });

// Build set_oldest_stored_round call
const oldest_round = 0;

const call = api.tx[stringCamelCase("Drand")][stringCamelCase("set_oldest_stored_round")](
  oldest_round
);

Runtime Info

View Source
Pallet Index
26
Call Index
2
First Version
v301
Current Version
v393
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