Index: src/build.c
==================================================================
--- src/build.c
+++ src/build.c
@@ -302,11 +302,11 @@
   ){
     struct sqlite3InitInfo sv = db->init;
     memset(&db->init, 0, sizeof(struct sqlite3InitInfo));
     rc = sqlite3InitOne(db, iDb, pzErr, 0);
     db->init = sv;
-    *pbUnload = (iDb!=1);
+    *pbUnload = (rc==SQLITE_OK && (iDb!=1));
   }
   return rc;
 }
 
 /*

Index: src/callback.c
==================================================================
--- src/callback.c
+++ src/callback.c
@@ -676,11 +676,11 @@
 
   if( p ) p->nRef++;
 
   /* If the SchemaPool contains one or more free schemas at the moment, 
   ** delete one of them. */
-  if( p->pSchema ){
+  if( p && p->pSchema ){
     Schema *pDel = p->pSchema;
     p->pSchema = pDel->pNext;
     schemaDelete(pDel);
   }
 
@@ -705,22 +705,21 @@
 ** schema-pool is not disconnected from. Or, if no OOM error occurs, 
 ** SQLITE_OK is returned.
 */
 int sqlite3SchemaDisconnect(sqlite3 *db, int iDb, int bNew){
   int rc = SQLITE_OK;
-  if( IsReuseSchema(db) && iDb!=1 ){
+  if( IsReuseSchema(db) ){
     Db *pDb = &db->aDb[iDb];
     SchemaPool *pSPool = pDb->pSPool;
     assert_schema_state_ok(db);
     assert( pDb->pSchema );
 
     if( pSPool==0 ){
       assert( pDb->pVTable==0 );
-      if( bNew==0 ){
-        schemaDelete(pDb->pSchema);
-        pDb->pSchema = 0;
-      }
+      assert( bNew==0 );
+      schemaDelete(pDb->pSchema);
+      pDb->pSchema = 0;
     }else{
       VTable *p;
       VTable *pNext;
       for(p=pDb->pVTable; p; p=pNext){
         pNext = p->pNext;
@@ -766,19 +765,17 @@
 ** as the only argument, if one is available. If one is not available, return
 ** NULL.
 */
 Schema *sqlite3SchemaExtract(SchemaPool *pSPool){
   Schema *pRet = 0;
-  if( pSPool ){
-    sqlite3_mutex_enter( sqlite3_mutex_alloc(SQLITE_MUTEX_STATIC_MASTER) );
-    if( pSPool->pSchema ){
-      pRet = pSPool->pSchema;
-      pSPool->pSchema = pRet->pNext;
-      pRet->pNext = 0;
-    }
-    sqlite3_mutex_leave( sqlite3_mutex_alloc(SQLITE_MUTEX_STATIC_MASTER) );
+  sqlite3_mutex_enter( sqlite3_mutex_alloc(SQLITE_MUTEX_STATIC_MASTER) );
+  if( pSPool->pSchema ){
+    pRet = pSPool->pSchema;
+    pSPool->pSchema = pRet->pNext;
+    pRet->pNext = 0;
   }
+  sqlite3_mutex_leave( sqlite3_mutex_alloc(SQLITE_MUTEX_STATIC_MASTER) );
   return pRet;
 }
 
 /*
 ** Return all sharable schemas held by database handle db back to their
@@ -809,13 +806,11 @@
 void sqlite3SchemaRelease(sqlite3 *db, int iDb){
   Db *pDb = &db->aDb[iDb];
   assert( iDb!=1 );
   assert_schema_state_ok(db);
   sqlite3_mutex_enter( sqlite3_mutex_alloc(SQLITE_MUTEX_STATIC_MASTER) );
-  if( pDb->pSPool && DbHasProperty(db, iDb, DB_SchemaLoaded) ){
-    schemaRelease(db, pDb);
-  }
+  schemaRelease(db, pDb);
   sqlite3_mutex_leave( sqlite3_mutex_alloc(SQLITE_MUTEX_STATIC_MASTER) );
 }
 
 /*
 ** In most cases, this function finds and returns the schema associated 
@@ -825,13 +820,15 @@
 ** sqlite3_malloc() is always returned.
 */
 Schema *sqlite3SchemaGet(sqlite3 *db, Btree *pBt){
   Schema *p;
   if( pBt && (db->openFlags & SQLITE_OPEN_SHARED_SCHEMA)==0 ){
-    p = (Schema *)sqlite3BtreeSchema(pBt, sizeof(Schema), sqlite3SchemaClear);
+    p = (Schema*)sqlite3BtreeSchema(pBt, sizeof(Schema), sqlite3SchemaClear);
   }else{
-    p = (Schema *)sqlite3DbMallocZero(0, sizeof(Schema));
+    db->lookaside.bDisable++;
+    p = (Schema*)sqlite3DbMallocZero(db, sizeof(Schema));
+    db->lookaside.bDisable--;
   }
   if( !p ){
     sqlite3OomFault(db);
   }else if ( 0==p->file_format ){
     sqlite3HashInit(&p->tblHash);

Index: src/prepare.c
==================================================================
--- src/prepare.c
+++ src/prepare.c
@@ -138,11 +138,14 @@
         assert( iDb==1 );
       }else{
         pData->rc = rc;
         if( rc==SQLITE_NOMEM ){
           sqlite3OomFault(db);
-        }else if( rc!=SQLITE_INTERRUPT && (rc&0xFF)!=SQLITE_LOCKED ){
+        }else if( rc!=SQLITE_INTERRUPT 
+               && (rc&0xFF)!=SQLITE_LOCKED 
+               && (rc&0xFF)!=SQLITE_IOERR
+        ){
           corruptSchema(pData, argv[0], sqlite3_errmsg(db));
         }
       }
     }
     sqlite3_finalize(pStmt);

Index: src/vdbe.c
==================================================================
--- src/vdbe.c
+++ src/vdbe.c
@@ -3290,17 +3290,10 @@
   assert( pOp->p5==0 || pOp->p4type==P4_INT32 );
   if( pOp->p5
    && (iMeta!=pOp->p3
       || db->aDb[pOp->p1].pSchema->iGeneration!=pOp->p4.i)
   ){
-    /*
-    ** IMPLEMENTATION-OF: R-03189-51135 As each SQL statement runs, the schema
-    ** version is checked to ensure that the schema has not changed since the
-    ** SQL statement was prepared.
-    */
-    sqlite3DbFree(db, p->zErrMsg);
-    p->zErrMsg = sqlite3DbStrDup(db, "database schema has changed");
     /* If the schema-cookie from the database file matches the cookie 
     ** stored with the in-memory representation of the schema, do
     ** not reload the schema from the database file.
     **
     ** If virtual-tables are in use, this is not just an optimization.
@@ -3313,10 +3306,17 @@
     ** a v-table method.
     */
     if( db->aDb[pOp->p1].pSchema->schema_cookie!=iMeta ){
       sqlite3ResetOneSchema(db, pOp->p1);
     }
+    /*
+    ** IMPLEMENTATION-OF: R-03189-51135 As each SQL statement runs, the schema
+    ** version is checked to ensure that the schema has not changed since the
+    ** SQL statement was prepared.
+    */
+    sqlite3DbFree(db, p->zErrMsg);
+    p->zErrMsg = sqlite3DbStrDup(db, "database schema has changed");
     p->expired = 1;
     rc = SQLITE_SCHEMA;
   }
   if( rc ) goto abort_due_to_error;
   break;

Index: test/reuse3.test
==================================================================
--- test/reuse3.test
+++ test/reuse3.test
@@ -271,7 +271,39 @@
 
 do_test 5.5 { 
   catchsql { SELECT nref,nschema FROM schemapool } db2
 } {0 {1 1}}
 
+db2 close
+db close
+do_test 5.6.1 {
+  forcedelete test.db2 test.db2-wal test.db2-journal
+  forcecopy test.db test.db2
+  sqlite3 db test.db
+  sqlite3 db2 test.db  -shared-schema 1
+  sqlite3 db3 test.db2 -shared-schema 1
+  register_schemapool_module db
+} {}
+
+do_execsql_test -db db2 5.6.2 { SELECT * FROM t1 }
+do_execsql_test -db db3 5.6.3 { SELECT * FROM t1 }
+do_execsql_test 5.6.4 {
+  SELECT 'nref=' || nRef, 'nschema=' || nSchema FROM schemapool; 
+  CREATE TABLE t4(x);
+  DROP TABLE t4;
+} {nref=2 nschema=1}
+do_execsql_test -db db2 5.6.5 { SELECT * FROM t1 }
+do_execsql_test -db db3 5.6.6 { SELECT * FROM t1 }
+do_execsql_test 5.6.7 {
+  SELECT 'nref=' || nRef, 'nschema=' || nSchema FROM schemapool; 
+  ATTACH 'test.db2' AS db2;
+  CREATE TABLE db2.t4(x);
+  DROP TABLE db2.t4;
+} {nref=1 nschema=1 nref=1 nschema=1}
+do_execsql_test -db db2 5.6.8 { SELECT * FROM t1 }
+do_execsql_test -db db3 5.6.9 { SELECT * FROM t1 }
+do_execsql_test 5.6.10 {
+  SELECT 'nref=' || nRef, 'nschema=' || nSchema FROM schemapool; 
+} {nref=2 nschema=1}
+
 finish_test
 

ADDED   test/reusefault.test
Index: test/reusefault.test
==================================================================
--- test/reusefault.test
+++ test/reusefault.test
@@ -0,0 +1,49 @@
+# 2019 February 12
+#
+# The author disclaims copyright to this source code.  In place of
+# a legal notice, here is a blessing:
+#
+#    May you do good and not evil.
+#    May you find forgiveness for yourself and forgive others.
+#    May you share freely, never taking more than you give.
+#
+#***********************************************************************
+#
+#
+
+set testdir [file dirname $argv0]
+source $testdir/tester.tcl
+set testprefix reusefault
+
+do_execsql_test 1.0 {
+  PRAGMA cache_size = 10;
+  CREATE TABLE t1(a UNIQUE, b UNIQUE);
+  INSERT INTO t1 VALUES(1, 2), (3, 4);
+}
+faultsim_save_and_close
+
+do_faultsim_test 1.1 -prep {
+  faultsim_restore
+  sqlite3 db test.db -shared-schema 1
+} -body {
+  execsql { SELECT * FROM t1 }
+} -test {
+  faultsim_test_result {0 {1 2 3 4}}
+}
+
+do_faultsim_test 1.2 -prep {
+  faultsim_restore
+  sqlite3 db test.db -shared-schema 1
+  execsql { SELECT * FROM t1 }
+  sqlite3 db2 test.db
+  db2 eval {CREATE TABLE a(a)}
+  db2 close
+} -body {
+  execsql { SELECT  * FROM t1 }
+} -test {
+  faultsim_test_result {0 {1 2 3 4}}
+}
+
+
+finish_test
+