SQLITE_BUSY

The SQLITE_BUSY result code indicates that the database file could not be written (or in some cases read) because of concurrent activity by some other database connection, usually a database connection in a separate process.

For example, if process A is in the middle of a large write transaction and at the same time process B attempts to start a new write transaction, process B will get back an SQLITE_BUSY result because SQLite only supports one writer at a time. Process B will need to wait for process A to finish its transaction before starting a new transaction. The sqlite3_busy_timeout() and sqlite3_busy_handler() interfaces and the busy_timeout pragma are available to process B to help it deal with SQLITE_BUSY errors.

An SQLITE_BUSY error can occur at any point in a transaction: when the transaction is first started, during any write or update operations, or when the transaction commits. To avoid encountering SQLITE_BUSY errors in the middle of a transaction, the application can use BEGIN IMMEDIATE instead of just BEGIN to start a transaction. The BEGIN IMMEDIATE command might itself return SQLITE_BUSY, but if it succeeds, then SQLite guarantees that no subsequent operations on the same database through the next COMMIT will return SQLITE_BUSY.

See also: SQLITE_BUSY_RECOVERY and SQLITE_BUSY_SNAPSHOT.

The SQLITE_BUSY result code differs from SQLITE_LOCKED in that SQLITE_BUSY indicates a conflict with a separate database connection, probably in a separate process, whereas SQLITE_LOCKED indicates a conflict within the same database connection (or sometimes a database connection with a shared cache).