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hrTooManyOpenTables
Why this is more specific than the message text
hrTooManyOpenTables means the workload exhausted open table/cursor capacity.
This is the legacy Directory Service backup/restore HRESULT form of JET_errTooManyOpenTables (0xC800051F).
The key comparison is: hrOutOfCursors is the broader cursor resource condition; this code is observed at table-open scale. The first useful observation is to count table opens by session and code path, including duplicates and temporary tables. This evidence identifies the exhausted pool so a leak, long transaction, concurrency spike, and hard capacity limit are not confused.
Related ESE conditions
hrTooManyOpenIndexes | the engine exhausted index descriptor blocks through excessive open/index-selection activity |
|---|---|
hrTooManySorts | temporary sort resources are exhausted by concurrent or unreleased sort operations |
hrTooManyOpenDatabases | a session or instance exceeded the number of simultaneously open databases |
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 workload exhausted open table/cursor capacity |
| First corrective direction | close request-scoped tables promptly and cap fan-out across concurrent work |
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.
Data for a reproducible case
- Code-specific observation: count table opens by session and code path, including duplicates and temporary tables.
- live resource counts grouped by session and request owner.
- relevant JET_param values and process or system capacity at first failure.
- the oldest transaction, longest-held cursor, or file growth operation retaining the resource.
Corrective workflow
- Freeze the failing request context and record
0xC800051F, the Jet API name, and the current instance/session ownership. - Verify the code-specific precondition: count table opens by session and code path, including duplicates and temporary tables.
- Apply the targeted fix: close request-scoped tables promptly and cap fan-out across concurrent work.
- Before retrying the operation, reconcile resource counts, owner cleanup, and capacity after the correction.
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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