Index: src/shell.c
==================================================================
--- src/shell.c
+++ src/shell.c
@@ -2630,10 +2630,13 @@
   "   -version             show SQLite version\n"
   "   -vfs NAME            use NAME as the default VFS\n"
 #ifdef SQLITE_ENABLE_VFSTRACE
   "   -vfstrace            enable tracing of all VFS calls\n"
 #endif
+#ifdef SQLITE_ENABLE_MULTIPLEX
+  "   -multiplex           enable the multiplexor VFS\n"
+#endif
 ;
 static void usage(int showDetail){
   fprintf(stderr,
       "Usage: %s [OPTIONS] FILENAME [SQL]\n"  
       "FILENAME is the name of an SQLite database. A new database is created\n"
@@ -2731,10 +2734,15 @@
          void *pOutArg,
          int makeDefault
       );
       vfstrace_register("trace",0,(int(*)(const char*,void*))fputs,stderr,1);
 #endif
+#ifdef SQLITE_ENABLE_MULTIPLEX
+    }else if( strcmp(argv[i],"-multiplex")==0 ){
+      extern int sqlite3_multiple_initialize(const char*,int);
+      sqlite3_multiplex_initialize(0, 1);
+#endif
     }else if( strcmp(argv[i],"-vfs")==0 ){
       sqlite3_vfs *pVfs = sqlite3_vfs_find(argv[++i]);
       if( pVfs ){
         sqlite3_vfs_register(pVfs, 1);
       }else{
@@ -2849,12 +2857,18 @@
       stdin_is_interactive = 0;
     }else if( strcmp(z,"-heap")==0 ){
       i++;
     }else if( strcmp(z,"-vfs")==0 ){
       i++;
+#ifdef SQLITE_ENABLE_VFSTRACE
     }else if( strcmp(z,"-vfstrace")==0 ){
       i++;
+#endif
+#ifdef SQLITE_ENABLE_MULTIPLEX
+    }else if( strcmp(z,"-multiplex")==0 ){
+      i++;
+#endif
     }else if( strcmp(z,"-help")==0 || strcmp(z, "--help")==0 ){
       usage(1);
     }else{
       fprintf(stderr,"%s: Error: unknown option: %s\n", Argv0, z);
       fprintf(stderr,"Use -help for a list of options.\n");

Index: src/test_multiplex.c
==================================================================
--- src/test_multiplex.c
+++ src/test_multiplex.c
@@ -43,10 +43,11 @@
 ** that do not support large files.
 */
 #include "sqlite3.h"
 #include <string.h>
 #include <assert.h>
+#include <stdlib.h>
 #include "test_multiplex.h"
 
 #ifndef SQLITE_CORE
   #define SQLITE_CORE 1  /* Disable the API redefinition in sqlite3ext.h */
 #endif
@@ -76,24 +77,30 @@
 #endif /* SQLITE_THREADSAFE==0 */
 
 
 /************************ Shim Definitions ******************************/
 
-#define SQLITE_MULTIPLEX_VFS_NAME "multiplex"
+#ifndef SQLITE_MULTIPLEX_VFS_NAME
+# define SQLITE_MULTIPLEX_VFS_NAME "multiplex"
+#endif
 
 /* This is the limit on the chunk size.  It may be changed by calling
 ** the xFileControl() interface.  It will be rounded up to a 
-** multiple of MAX_PAGE_SIZE.  We default it here to 1GB.
+** multiple of MAX_PAGE_SIZE.  We default it here to 2GiB less 64KiB.
 */
-#define SQLITE_MULTIPLEX_CHUNK_SIZE (MAX_PAGE_SIZE*16384)
+#ifndef SQLITE_MULTIPLEX_CHUNK_SIZE
+# define SQLITE_MULTIPLEX_CHUNK_SIZE 2147418112
+#endif
 
 /* Default limit on number of chunks.  Care should be taken
 ** so that values for chunks numbers fit in the SQLITE_MULTIPLEX_EXT_FMT
 ** format specifier. It may be changed by calling
 ** the xFileControl() interface.
 */
-#define SQLITE_MULTIPLEX_MAX_CHUNKS 32
+#ifndef SQLITE_MULTIPLEX_MAX_CHUNKS
+# define SQLITE_MULTIPLEX_MAX_CHUNKS 32
+#endif
 
 /* If SQLITE_MULTIPLEX_EXT_OVWR is defined, the 
 ** last SQLITE_MULTIPLEX_EXT_SZ characters of the 
 ** filename will be overwritten, otherwise, the 
 ** multiplex extension is simply appended to the filename.
@@ -429,16 +436,22 @@
       rc=SQLITE_NOMEM;
     }
   }
 
   if( rc==SQLITE_OK ){
+    const char *zChunkSize;
     /* assign pointers to extra space allocated */
     char *p = (char *)&pGroup[1];
     pMultiplexOpen->pGroup = pGroup;
     memset(pGroup, 0, sz);
     pGroup->bEnabled = -1;
     pGroup->nChunkSize = SQLITE_MULTIPLEX_CHUNK_SIZE;
+    zChunkSize = sqlite3_uri_parameter(zName, "chunksize");
+    if( zChunkSize ){
+      int n = atoi(zChunkSize);
+      if( n>0 ) pGroup->nChunkSize = (n+0xffff)&~0xffff;
+    }
     pGroup->nMaxChunks = SQLITE_MULTIPLEX_MAX_CHUNKS;
     pGroup->pReal = (sqlite3_file **)p;
     p += (sizeof(sqlite3_file *)*pGroup->nMaxChunks);
     for(i=0; i<pGroup->nMaxChunks; i++){
       pGroup->pReal[i] = (sqlite3_file *)p;