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Mar 11, 2025
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Query resources and storage access timeout #1180

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andrejtonev Mar 7, 2025
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access timeout
andrejtonev Mar 11, 2025
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andrejtonev Mar 11, 2025
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katarinasupe Mar 11, 2025
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29 changes: 28 additions & 1 deletion pages/help-center/errors/transactions.mdx
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Expand Up @@ -12,6 +12,7 @@ import {CommunityLinks} from '/components/social-card/CommunityLinks'
While working with Memgraph, you can encounter various transaction errors. Here are some of them, along with the instructions on how to handle them:
- [Conflicting transactions](#conflicting-transaction)
- [Transaction timeout](#transaction-timeout)
- [Storage access timeout](#storage-access-timeout)

## Conflicting transactions

Expand Down Expand Up @@ -112,5 +113,31 @@ To change that, update the flag `--query-execution-timeout-sec` value to a value

Here are the [instructions](/configuration/configuration-settings#using-flags-and-config-file) on how to update the configuration.

## Storage access timeout

<CommunityLinks/>
### Error messages

Here are the storage access error messages you might encounter:

1. **Cannot access storage, unique access query is running. Try again later.**
2. **Cannot get unique access to the storage. Try stopping other queries that are running in parallel.**

### Understanding storage access timeout

Storage access timeouts occur during query preparation when the query execution engine cannot get the required type of access to the storage. There are two types of storage access:

- **Shared access**: Multiple queries can have shared access at the same time, but shared access cannot be granted while a query with unique access is running.
- **Unique access**: Only one query can have unique access at a time, and no other query can have any type of access during that period.

These timeouts prevent worker starvation and database blocking that could occur if queries were to wait indefinitely for storage access.

### Handling storage access timeout

When you encounter a storage access timeout:

1. Check for long-running queries that might be blocking storage access.
2. Consider breaking down complex queries that require unique access into smaller operations.
3. Retry the query after other queries have completed.
4. If possible, schedule queries requiring unique access during periods of lower database activity.

<CommunityLinks/>