diff --git a/openjpa-jdbc/src/main/java/org/apache/openjpa/jdbc/kernel/exps/TypecastAsNumber.java b/openjpa-jdbc/src/main/java/org/apache/openjpa/jdbc/kernel/exps/TypecastAsNumber.java
index d7c44faa14..4558e228f7 100644
--- a/openjpa-jdbc/src/main/java/org/apache/openjpa/jdbc/kernel/exps/TypecastAsNumber.java
+++ b/openjpa-jdbc/src/main/java/org/apache/openjpa/jdbc/kernel/exps/TypecastAsNumber.java
@@ -160,7 +160,7 @@ public void appendTo(Select sel, ExpContext ctx, ExpState state, SQLBuffer sql,
         sql.append(part1);
         _val.appendTo(sel, ctx, etnstate.valueState, sql, 0);
         sql.append(part2);
-        sql.append(getDbNumberTargetTypeName(dict));
+        sql.append(dict.getNumberCastTypeName(getType()));
         sql.append(part3);
     }
 
@@ -175,23 +175,4 @@ public void acceptVisit(ExpressionVisitor visitor) {
     public int getId() {
         return Val.EXTRACTDTF_VAL;
     }
-
-    private static String sanitize(String type) {
-        final int idx = type.indexOf('{');
-        return idx < 0 ? type : type.substring(0, idx);
-    }
-
-    private String getDbNumberTargetTypeName(DBDictionary dict) {
-        String type;
-        if (getType() == int.class) {
-            type = dict.integerCastTypeName;
-        } else if (getType() == long.class) {
-            type = dict.decimalTypeName;
-        } else if (getType() == float.class) {
-            type = dict.floatTypeName;
-        } else {
-            type = dict.doubleTypeName;
-        }
-        return sanitize(type);
-    }
 }
diff --git a/openjpa-jdbc/src/main/java/org/apache/openjpa/jdbc/kernel/exps/TypecastAsString.java b/openjpa-jdbc/src/main/java/org/apache/openjpa/jdbc/kernel/exps/TypecastAsString.java
index a4fb69b2a2..1db505ea77 100644
--- a/openjpa-jdbc/src/main/java/org/apache/openjpa/jdbc/kernel/exps/TypecastAsString.java
+++ b/openjpa-jdbc/src/main/java/org/apache/openjpa/jdbc/kernel/exps/TypecastAsString.java
@@ -148,11 +148,7 @@ public void appendTo(Select sel, ExpContext ctx, ExpState state,
         sql.append(part1);
         _val.appendTo(sel, ctx, casstate.valueState, sql, 0);
         sql.append(part2);
-        if (dict.supportsUnsizedCharOnCast) {
-            sql.append(dict.varcharTypeName);
-        } else {
-            sql.append(dict.typecastToStringTypeName + "(" + dict.characterColumnSize + ")");
-        }
+        sql.append(dict.getStringCastTypeName());
         sql.append(part3);
     }
 
diff --git a/openjpa-jdbc/src/main/java/org/apache/openjpa/jdbc/sql/DBDictionary.java b/openjpa-jdbc/src/main/java/org/apache/openjpa/jdbc/sql/DBDictionary.java
index 95f6bb573a..da5cdd38ab 100644
--- a/openjpa-jdbc/src/main/java/org/apache/openjpa/jdbc/sql/DBDictionary.java
+++ b/openjpa-jdbc/src/main/java/org/apache/openjpa/jdbc/sql/DBDictionary.java
@@ -18,6 +18,8 @@
  */
 package org.apache.openjpa.jdbc.sql;
 
+import static java.util.Locale.ROOT;
+
 import java.io.BufferedReader;
 import java.io.ByteArrayInputStream;
 import java.io.CharArrayReader;
@@ -142,8 +144,6 @@
 import org.apache.openjpa.util.UnsupportedException;
 import org.apache.openjpa.util.UserException;
 
-import static java.util.Locale.ROOT;
-
 
 /**
  * Class which allows the creation of SQL dynamically, in a
@@ -511,7 +511,24 @@ public enum DateMillisecondBehaviors { DROP, ROUND, RETAIN }
 
     public boolean supportsUnsizedCharOnCast = true;
 
-    public String integerCastTypeName = integerTypeName;
+    /**
+     * Type name used as the target of a CAST to a 32 bit integer.
+     * <p>
+     * Note: this is a field initializer, so it is evaluated before any subclass constructor runs.
+     * Dictionaries which change {@link #integerTypeName} do <em>not</em> implicitly change this value.
+     * Set it explicitly if the DDL type name is not a valid CAST target.
+     */
+    public String integerCastTypeName = null;
+
+    /**
+     * Type name used as the target of a CAST to a 64 bit integer.
+     * <p>
+     * If <code>null</code> (the default), {@link #bigintTypeName} is resolved lazily by
+     * {@link #getLongCastTypeName()}. Resolving lazily rather than in a field initializer is deliberate:
+     * several dictionaries assign {@link #bigintTypeName} in their constructor or even in
+     * {@link #connectedConfiguration(java.sql.Connection)}, which happens after field initialization.
+     */
+    public String longCastTypeName = null;
 
     // Naming utility and naming rules
     private DBIdentifierUtil namingUtil = null;
@@ -2223,6 +2240,51 @@ protected int getDateFractionDigits(Column col, String typeName) {
         return dateFractionDigits;
     }
 
+    /**
+     * Return the type name to use as the target of a CAST to a 32 bit integer.
+     * Defaults to {@link #integerTypeName} unless {@link #integerCastTypeName} was set explicitly.
+     */
+    public String getIntegerCastTypeName() {
+        return integerCastTypeName == null ? integerTypeName : integerCastTypeName;
+    }
+
+    /**
+     * Return the type name to use as the target of a CAST to a 64 bit integer.
+     * Defaults to {@link #bigintTypeName} unless {@link #longCastTypeName} was set explicitly.
+     */
+    public String getLongCastTypeName() {
+        return longCastTypeName == null ? bigintTypeName : longCastTypeName;
+    }
+
+    /**
+     * Return the type name to use as the target of a CAST of a numeric value to the given java type.
+     * Any DDL size marker (<code>{0}</code>) is stripped, as CAST targets are not sized by the schema.
+     */
+    public String getNumberCastTypeName(Class<?> type) {
+        String name;
+        if (type == int.class || type == Integer.class) {
+            name = getIntegerCastTypeName();
+        } else if (type == long.class || type == Long.class) {
+            name = getLongCastTypeName();
+        } else if (type == float.class || type == Float.class) {
+            name = floatTypeName;
+        } else {
+            name = doubleTypeName;
+        }
+        return insertSize(name, null);
+    }
+
+    /**
+     * Return the type name to use as the target of a CAST to a string.
+     * Any DDL size marker (<code>{0}</code>) is stripped.
+     */
+    public String getStringCastTypeName() {
+        if (supportsUnsizedCharOnCast) {
+            return insertSize(varcharTypeName, null);
+        }
+        return insertSize(typecastToStringTypeName, null) + "(" + characterColumnSize + ")";
+    }
+
     /**
      * Helper method that inserts a size clause for a given SQL type.
      *
@@ -5302,27 +5364,32 @@ public void startConfiguration() {
     @Override
     public void endConfiguration() {
         // add additional reserved words set by user
-        if (reservedWords != null)
+        if (reservedWords != null) {
             reservedWordSet.addAll(Arrays.asList(StringUtil.split(reservedWords.toUpperCase(Locale.ENGLISH), ",", 0)));
+        }
 
         // add system schemas set by user
-        if (systemSchemas != null)
+        if (systemSchemas != null) {
             systemSchemaSet.addAll(Arrays.asList(StringUtil.split(systemSchemas.toUpperCase(Locale.ENGLISH), ",", 0)));
+        }
 
         // add system tables set by user
-        if (systemTables != null)
+        if (systemTables != null) {
             systemTableSet.addAll(Arrays.asList(StringUtil.split(systemTables.toUpperCase(Locale.ENGLISH), ",", 0)));
+        }
 
         // add fixed size type names set by the user
-        if (fixedSizeTypeNames != null)
+        if (fixedSizeTypeNames != null) {
             fixedSizeTypeNameSet.addAll(Arrays.asList(StringUtil.split(fixedSizeTypeNames.toUpperCase(Locale.ENGLISH), ",", 0)));
+        }
 
         // if user has unset sequence sql, null it out so we know sequences
         // aren't supported
         nextSequenceQuery = StringUtil.trimToNull(nextSequenceQuery);
 
-        if (selectWords != null)
+        if (selectWords != null) {
             selectWordSet.addAll(Arrays.asList(StringUtil.split(selectWords.toUpperCase(Locale.ENGLISH), ",", 0)));
+        }
 
         if (invalidColumnWordSet.isEmpty()) {
             Collection<String> invalidColumns = loadFromResource("sql-invalid-column-names.rsrc");
diff --git a/openjpa-jdbc/src/main/java/org/apache/openjpa/jdbc/sql/MariaDBDictionary.java b/openjpa-jdbc/src/main/java/org/apache/openjpa/jdbc/sql/MariaDBDictionary.java
index f1c5d834b3..a88fe887f9 100644
--- a/openjpa-jdbc/src/main/java/org/apache/openjpa/jdbc/sql/MariaDBDictionary.java
+++ b/openjpa-jdbc/src/main/java/org/apache/openjpa/jdbc/sql/MariaDBDictionary.java
@@ -181,6 +181,8 @@ public MariaDBDictionary() {
 
         dateFractionDigits = 0;
         supportsUnsizedCharOnCast = false;
+        // MariaDB has no BIGINT cast target; SIGNED [INTEGER] yields a 64 bit signed value
+        longCastTypeName = "SIGNED";
     }
 
     @Override
diff --git a/openjpa-jdbc/src/main/java/org/apache/openjpa/jdbc/sql/MySQLDictionary.java b/openjpa-jdbc/src/main/java/org/apache/openjpa/jdbc/sql/MySQLDictionary.java
index 11dda26988..be69d0b39a 100644
--- a/openjpa-jdbc/src/main/java/org/apache/openjpa/jdbc/sql/MySQLDictionary.java
+++ b/openjpa-jdbc/src/main/java/org/apache/openjpa/jdbc/sql/MySQLDictionary.java
@@ -180,6 +180,8 @@ public MySQLDictionary() {
         dateFractionDigits = 0;
         supportsUnsizedCharOnCast = false;
         integerCastTypeName = "SIGNED";
+        // MySQL has no BIGINT cast target; SIGNED [INTEGER] yields a 64 bit signed value
+        longCastTypeName = "SIGNED";
     }
 
     @Override
diff --git a/openjpa-jdbc/src/test/java/org/apache/openjpa/jdbc/sql/TestCastTypeNames.java b/openjpa-jdbc/src/test/java/org/apache/openjpa/jdbc/sql/TestCastTypeNames.java
new file mode 100644
index 0000000000..018e8e51a8
--- /dev/null
+++ b/openjpa-jdbc/src/test/java/org/apache/openjpa/jdbc/sql/TestCastTypeNames.java
@@ -0,0 +1,85 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+package org.apache.openjpa.jdbc.sql;
+
+import static org.junit.Assert.assertEquals;
+
+import org.junit.Test;
+
+/**
+ * Verifies the type names rendered as the target of a SQL CAST, see OPENJPA-2966.
+ */
+public class TestCastTypeNames {
+
+    /**
+     * A 64 bit value must not be cast to an unsized DECIMAL: that defaults to DECIMAL(10,0) on
+     * MySQL/MariaDB (silent truncation) and to DECIMAL(5,0) on Derby (SQLState 22003).
+     */
+    @Test
+    public void testLongCastTypeName() {
+        assertEquals("BIGINT", new DBDictionary().getNumberCastTypeName(long.class));
+        assertEquals("BIGINT", new DerbyDictionary().getNumberCastTypeName(long.class));
+        assertEquals("BIGINT", new H2Dictionary().getNumberCastTypeName(long.class));
+        assertEquals("BIGINT", new PostgresDictionary().getNumberCastTypeName(long.class));
+        assertEquals("BIGINT", new DB2Dictionary().getNumberCastTypeName(long.class));
+
+        // MySQL and MariaDB do not accept BIGINT as a CAST target, SIGNED [INTEGER] is 64 bit there
+        assertEquals("SIGNED", new MySQLDictionary().getNumberCastTypeName(long.class));
+        assertEquals("SIGNED", new MariaDBDictionary().getNumberCastTypeName(long.class));
+
+        // size markers of the DDL type name must not leak into the CAST
+        assertEquals("NUMBER", new OracleDictionary().getNumberCastTypeName(long.class));
+    }
+
+    /**
+     * The cast type name is resolved lazily, so a dictionary which assigns its DDL type name after
+     * field initialisation (e.g. DB2 z/OS v8 in connectedConfiguration()) is honoured.
+     */
+    @Test
+    public void testLongCastTypeNameIsResolvedLazily() {
+        DBDictionary dict = new DB2Dictionary();
+        dict.bigintTypeName = "DECIMAL(31,0)";
+        assertEquals("DECIMAL(31,0)", dict.getNumberCastTypeName(long.class));
+
+        dict.longCastTypeName = "SIGNED";
+        assertEquals("SIGNED", dict.getNumberCastTypeName(long.class));
+    }
+
+    @Test
+    public void testOtherNumberCastTypeNames() {
+        assertEquals("INTEGER", new DBDictionary().getNumberCastTypeName(int.class));
+        assertEquals("SIGNED", new MySQLDictionary().getNumberCastTypeName(int.class));
+        assertEquals("NUMBER", new OracleDictionary().getNumberCastTypeName(int.class)); // tests lazy inint
+        assertEquals("FLOAT", new DBDictionary().getNumberCastTypeName(float.class));
+        assertEquals("DOUBLE", new DBDictionary().getNumberCastTypeName(double.class));
+    }
+
+    /**
+     * The string cast must strip the DDL size marker as well - FoxPro used to render
+     * CAST(x AS CHARACTER{0}).
+     */
+    @Test
+    public void testStringCastTypeName() {
+        assertEquals("VARCHAR", new DBDictionary().getStringCastTypeName());
+        assertEquals("CHARACTER", new FoxProDictionary().getStringCastTypeName());
+        assertEquals("CHAR(255)", new MySQLDictionary().getStringCastTypeName());
+        assertEquals("CHAR(255)", new MariaDBDictionary().getStringCastTypeName());
+        assertEquals("VARCHAR(255)", new OracleDictionary().getStringCastTypeName());
+    }
+}