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hrTooManyAttachedDatabases
Where the operation crossed the contract
hrTooManyAttachedDatabases means the instance reached its attached-database limit.
This is the legacy Directory Service backup/restore HRESULT form of JET_errTooManyAttachedDatabases (0xC800070D).
The key comparison is: hrTooManyOpenDatabases is per-session/open-handle pressure; attachment is an instance-level relationship. The first useful observation is to enumerate attached paths, open state, detach failures, and instance ownership. This evidence identifies the exhausted pool so a leak, long transaction, concurrency spike, and hard capacity limit are not confused.
Reconstruct the engine state
- Code-specific observation: enumerate attached paths, open state, detach failures, and instance ownership.
- relevant JET_param values and process or system capacity at first failure; associate it with this result rather than with a later generic exception.
- the oldest transaction, longest-held cursor, or file growth operation retaining the resource; associate it with this result rather than with a later generic exception.
- live resource counts grouped by session and request owner.
The ESE objects in play
| Diagnostic layer | bounded engine, process, and storage resources |
|---|---|
| Typical API surface | instance system parameters, sessions, cursors, temporary tables, database attachment, and file growth |
| Code-specific condition | the instance reached its attached-database limit |
| First corrective direction | detach databases no longer needed or partition the workload across intentionally separate instances |
Long transactions can retain versions and indirectly amplify memory and log pressure. A retry without closing owners or adding capacity often repeats the same failure and increases load.
Repair without destroying evidence
- Freeze the failing request context and record
0xC800070D, the Jet API name, and the current instance/session ownership. - Verify the code-specific precondition: enumerate attached paths, open state, detach failures, and instance ownership.
- Apply the targeted fix: detach databases no longer needed or partition the workload across intentionally separate instances.
- Before retrying the operation, reconcile resource counts, owner cleanup, and capacity after the correction.
Do not collapse these codes together
hrTooManyActiveUsers | the engine reached its active-user or concurrent-session workload limit |
|---|---|
hrTooManyOpenDatabases | a session or instance exceeded the number of simultaneously open databases |
hrOutOfSessions | the instance cannot allocate another JET_SESID |
Actions that can hide or worsen the problem
- Do not raise limits before checking ownership and release paths.
- Do not create a retry storm while the exhausted resource remains unavailable.
Technical references
- JET_param enumeration.
- Transactions and save points
- ESE files and storage paths
- ESE source repository
- Microsoft: JET_ERR enumeration
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