SQLite

      /* On an attach, also set the journal mode.  Note that
      ** sqlite3VdbeUsesBtree() is not call here since the iDb index
      ** will be out of range prior to the new database being attached.
      ** The OP_JournalMode opcode will all sqlite3VdbeUsesBtree() for us.
      */
      sqlite3VdbeAddOp3(v, OP_JournalMode, db->nDb, regArgs+3, 
                           db->dfltJournalMode);
      sqlite3VdbeChangeP5(v, 1);
    }

    /* Code an OP_Expire. For an ATTACH statement, set P1 to true (expire this
    ** statement only). For DETACH, set it to false (expire all existing
    ** statements).
    */
    sqlite3VdbeAddOp1(v, OP_Expire, (type==SQLITE_ATTACH));

*/
case OP_Checkpoint: {
  rc = sqlite3Checkpoint(db, pOp->p1);
  break;
};  
#endif

/* Opcode: JournalMode P1 P2 P3 * P5
**
** Change the journal mode of database P1 to P3. P3 must be one of the
** PAGER_JOURNALMODE_XXX values. If changing between the various rollback
** modes (delete, truncate, persist, off and memory), this is a simple
** operation. No IO is required.
**
** If changing into or out of WAL mode the procedure is more complicated.
**
** Write a string containing the final journal-mode to register P2.
**
** If an attempt to change in to or out of WAL mode fails because another
** connection also has the same database open, then an SQLITE_BUSY error
** is raised if P5==0, or of P5!=0 the journal mode changed is skipped
** without signaling the error.
*/
case OP_JournalMode: {    /* out2-prerelease */
  Btree *pBt;                     /* Btree to change journal mode of */
  Pager *pPager;                  /* Pager associated with pBt */
  int eNew;                       /* New journal mode */
  int eOld;                       /* The old journal mode */
  const sqlite3_vfs *pVfs;        /* The VFS of pPager */

        if( eOld==PAGER_JOURNALMODE_WAL ){
          /* If leaving WAL mode, close the log file. If successful, the call
          ** to PagerCloseWal() checkpoints and deletes the write-ahead-log 
          ** file. An EXCLUSIVE lock may still be held on the database file 
          ** after a successful return. 
          */
          rc = sqlite3PagerCloseWal(pPager);
          if( rc==SQLITE_OK ){
            sqlite3PagerJournalMode(pPager, eNew);
          }else if( rc==SQLITE_BUSY && pOp->p5==0 ){
            goto abort_due_to_error;
          }
        }else{
          sqlite3PagerJournalMode(pPager, PAGER_JOURNALMODE_DELETE);
          rc = SQLITE_OK;
        }
  
        /* Open a transaction on the database file. Regardless of the journal
        ** mode, this transaction always uses a rollback journal.
        */
        assert( sqlite3BtreeIsInTrans(pBt)==0 );
        if( rc==SQLITE_OK ){
          rc = sqlite3BtreeSetVersion(pBt, 
                                      (eNew==PAGER_JOURNALMODE_WAL ? 2 : 1));
          if( rc==SQLITE_BUSY && pOp->p5==0 ) goto abort_due_to_error;
        }else if( rc==SQLITE_BUSY ){
          rc = SQLITE_OK;
        }
      }
    }
  }
#endif /* ifndef SQLITE_OMIT_WAL */

  eNew = sqlite3PagerJournalMode(pPager, eNew);
  pOut = &aMem[pOp->p2];