OperationalError: database is locked

Question

I have made some repetitive operations in my application (testing it), and suddenly I’m getting a weird error:

OperationalError: database is locked

I've restarted the server, but the error persists. What can it be all about?

Answer 1

try this command:

sudo fuser -k 8000/tcp

Answer 2

From django doc:

SQLite is meant to be a lightweight database, and thus can't support a high level of concurrency. OperationalError: database is locked errors indicate that your application is experiencing more concurrency than sqlite can handle in default configuration. This error means that one thread or process has an exclusive lock on the database connection and another thread timed out waiting for the lock the be released.

Python's SQLite wrapper has a default timeout value that determines how long the second thread is allowed to wait on the lock before it times out and raises the OperationalError: database is locked error.

If you're getting this error, you can solve it by:

Switching to another database backend. At a certain point SQLite becomes too "lite" for real-world applications, and these sorts of concurrency errors indicate you've reached that point.

Rewriting your code to reduce concurrency and ensure that database transactions are short-lived.

Increase the default timeout value by setting the timeout database option optionoption

http://docs.djangoproject.com/en/dev/ref/databases/#database-is-locked-errorsoption

Answer 3

In my case, It was because I open the database from SQLite Browser. When I close it from the browser, the problem is gone.

Answer 4

I disagree with @Patrick's answer which, by quoting this doc, implicitly links OP's problem (Database is locked) to this:

Switching to another database backend. At a certain point SQLite becomes too "lite" for real-world applications, and these sorts of concurrency errors indicate you've reached that point.

This is a bit "too easy" to incriminate SQlite for this problem. Unless you have a very busy server with thousands of connections at the same second, the reason for this Database is locked error is probably more a bad use of the API, than a problem inherent to SQlite which would be "too light". Here are more informations about Implementation Limits for SQLite.

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Now the solution:

I had the same problem when I was using two scripts using the same database at the same time:

• one was accessing the DB with write operations
• the other was accessing the DB in read-only

Solution: always do cursor.close() as soon as possible after having done a (even read-only) query.

Here are more details.

Answer 5

In my case, I had not saved a database operation I performed within the SQLite Browser. Saving it solved the issue.

Answer 6

The practical reason for this is often that the python or django shells have opened a request to the DB and it wasn't closed properly; killing your terminal access often frees it up. I had this error on running command line tests today.

Edit: I get periodic upvotes on this. If you'd like to kill access without rebooting the terminal, then from commandline you can do:

from django import db
db.connections.close_all()