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This information is obsolete. You are looking at the CVSTrac source management system display for SQLite that was replaced by Fossil on 2009-08-11. The information shown here has not been updated since that cut-over. These pages are retained for historical reference only.

Error Code SQLITE_LOCKED (6): Database Is Locked

This error code occurs when you try to do two incompatible things with a database at the same time from the same database connection. For example, if you are in the middle of a SELECT statement and you try to DROP one of the tables being read by the SELECT, you will get an SQLITE_LOCKED error. Here is an example (using Tcl):

   db eval {SELECT rowid FROM ex1} {
     if {$rowid==10} {
       db eval {DROP TABLE ex1}  ;# will give SQLITE_LOCKED error
     }
   }

Note that an SQLITE_LOCKED error is distinct from SQLITE_BUSY (5). SQLITE_BUSY means that another database connection (probably in another process) is using the database in a way that prevents you from using it. SQLITE_LOCKED means the source of contention is internal and comes from the same database connection that received the SQLITE_LOCKED error.

Here are other reasons for getting an SQLITE_LOCKED error:

  1. Trying to CREATE or DROP a table or index while a SELECT statement is still pending.

    • Sometimes people think they have finished with a SELECT statement because sqlite3_step() has returned SQLITE_DONE. But the SELECT is not really complete until sqlite3_reset() or sqlite3_finalize() have been called.

  2. Trying to write to a table while a SELECT is active on that same table.

    • As of check-in [3355] (2006-08-16 after version 3.3.7) this is now allowed.

  3. Trying to do two SELECT on the same table at the same time in a multithread application, if sqlite is not set to do so.

(can someone please expand on the 'not set to do so' above?)