2.2. Table Level Locking  ... Tables support two types of locks, "read-locks" and "write-locks". Locks are granted to connections - at any one time, each database connection has either a read-lock, write-lock or no lock on each database table. At any one ... 

 ... If a "DROP TABLE" or "DROP INDEX" SQL command is executed, and the same database connection currently has one or more actively executing SELECT statements, then SQLITE_LOCKED is returned. If sqlite3_unlock_notify() is called in this case, then the specified callback ... 

sqlite3_unlock_notify()

When running in shared-cache mode, a database operation may fail with an SQLITE_LOCKED error if the required locks on the shared-cache or individual tables within the shared-cache cannot be obtained. See SQLite Shared-Cache Mode for a ... 

sqlite3_busy_handler()

 ... attempt is made to access a database table associated with database connection D when another thread or process has the table locked. The sqlite3_busy_handler() interface is used to implement sqlite3_busy_timeout() and PRAGMA busy_timeout. If the busy callback is NULL, then ... 

 ... File Lifecycles When a WAL mode database is in active use, all three of the above files usually exist. Except, the Wal-Index file is omitted if exclusive locking mode is set. If the last client using the database shuts ... 

3.2. Acquiring A Read Lock  ... table so that it can know how to parse the INSERT statements and discover where in the database file the new information should be stored. The first step toward reading from the database file is obtaining a shared lock on ... 

sqlite3_busy_timeout()

This routine sets a busy handler that sleeps for a specified amount of time when a table is locked. The handler will sleep multiple times until at least "ms" milliseconds of sleeping have accumulated. After at least "ms" milliseconds of ... 

6. Result Code Meanings  ... For example, a DROP TABLE statement cannot be run while another thread is reading from that table on the same database connection because dropping the table would delete the table out from under the concurrent reader. The SQLITE_LOCKED result code ... 

 ... abort */ #define SQLITE_BUSY 5 /* The database file is locked */ #define SQLITE_LOCKED 6 /* A table in the database is locked */ #define SQLITE_NOMEM 7 /* A malloc() failed */ #define SQLITE_READONLY 8 /* Attempt to write a readonly database */ #define SQLITE_INTERRUPT 9 /* Operation terminated by ... 

 ... A more detailed report on the locking behavior of SQLite version 3.0 is available separately. A limited form of table-level locking is now also available in SQLite. If each table is stored in a separate database file, those ...