Immutability

WORM (Write Once, Read Many) storage allows data to be written a single time and then read repeatedly but never altered or deleted before its retention period expires. WORM is a core requirement of regulations such as SEC Rule 17a-4 because it makes archived records tamper-evident and immutable.

A retention policy is a set of rules defining how long each category of record must be kept and what happens when that period ends. Retention schedules are driven by regulation, legal exposure, and business need, and they underpin both compliance and defensible deletion.

Defensible deletion is the documented, policy-driven disposal of data that has met its retention requirement and is not subject to any legal hold. Done correctly — with consistent policies and audit trails — it reduces storage cost, risk, and discovery scope while standing up to legal scrutiny.

Single-instance storage, or deduplication, stores only one copy of identical content (such as a message sent to many recipients or a repeated attachment) while preserving each reference. It reduces archive size and cost without losing any record.