VMware Blockchain nodes have a limited local persistent storage capacity. The local persistent storage cannot save the complete history of a blockchain because it requires massive storage resources to save the history of high-volume clearing and settlement transactions.
The DAML execution engine on the Replica nodes determines which key values are stale. As part of executing a transaction, the execution engine tags the stale key values. These stale key values continue to remain in the local persistent storage for a two-week window. After the time frame expires, the stale key values are pruned. Depending on the requirements, the two-week window time frame for pruning can be reduced or increased.
To avoid performance problems due to a lack of storage resources, it is essential to securely back up and delete stale key values and free up storage space on the nodes. The process of deleting stale key values from the VMware Blockchain nodes is called pruning.
Data pruning is irreversible. After the data is pruned from the Replica nodes, the data is no longer available to the Client nodes. As a best practice, back up the Replica nodes and Client nodes before initiating a pruning process.
See the VMware Blockchain Back Up and Restore chapter in the Using and Managing VMware Blockchain guide to back up your data.