Overflow Events

The first 100,000 changes generate change events. The set of changes beyond that generate an overflow event. An overflow event is generated when a single transaction contains more than 100,000 changes. An overflow event contains only header fields. The changeType field header value is GAP_OVERFLOW instead of the specific type of change. The object type corresponding to the change is in the entityName field. An overflow event doesn’t include details about the change, such as the record fields or record ID.

A record creation, deletion, or undeletion is counted as one change toward the threshold. However, in a record update, each field change is counted toward the overflow threshold. For example, if three field values are modified in one record update, they count as three operations against the overflow threshold.

Transactions with a high volume of operations are not frequent, but they can occur in some situations, such as for a recurring event with hundreds of occurrences and hundreds of attendees. Another example is a cascade delete of accounts that are associated with many opportunities, contacts, and activities, which results in deleting many more records in the same transaction. If the cascade delete results in the deletion of 120,000 account, opportunity, contact, and activity records in the same transaction, the deletions of the first 100,000 records generate delete change events, and the remaining 20,000 records generate overflow events.