Add migration script to use characters instead of bytes for oracle db

Resolves BATCH-2091

spring-batch-core/src/main/resources/org/springframework/batch/core/migration/4.1/migration-oracle10g.sql

@@ -0,0 +1,19 @@
+ALTER TABLE BATCH_JOB_INSTANCE MODIFY JOB_NAME VARCHAR2(100 char);
+ALTER TABLE BATCH_JOB_INSTANCE MODIFY JOB_KEY VARCHAR2(32 char);
+
+ALTER TABLE BATCH_JOB_EXECUTION MODIFY STATUS VARCHAR2(10 char);
+ALTER TABLE BATCH_JOB_EXECUTION MODIFY EXIT_CODE VARCHAR2(2500 char);
+ALTER TABLE BATCH_JOB_EXECUTION MODIFY EXIT_MESSAGE VARCHAR2(2500 char);
+ALTER TABLE BATCH_JOB_EXECUTION MODIFY JOB_CONFIGURATION_LOCATION VARCHAR2(2500 char);
+
+ALTER TABLE BATCH_JOB_EXECUTION_PARAMS MODIFY TYPE_CD VARCHAR2(6 char);
+ALTER TABLE BATCH_JOB_EXECUTION_PARAMS MODIFY KEY_NAME VARCHAR2(100 char);
+ALTER TABLE BATCH_JOB_EXECUTION_PARAMS MODIFY STRING_VAL VARCHAR2(250 char);
+
+ALTER TABLE BATCH_STEP_EXECUTION MODIFY STEP_NAME VARCHAR2(100 char);
+ALTER TABLE BATCH_STEP_EXECUTION MODIFY STATUS VARCHAR2(10 char);
+ALTER TABLE BATCH_STEP_EXECUTION MODIFY EXIT_CODE VARCHAR2(2500 char);
+ALTER TABLE BATCH_STEP_EXECUTION MODIFY EXIT_MESSAGE VARCHAR2(2500 char);
+
+ALTER TABLE BATCH_STEP_EXECUTION_CONTEXT MODIFY SHORT_CONTEXT VARCHAR2(2500 char);
+ALTER TABLE BATCH_JOB_EXECUTION_CONTEXT MODIFY SHORT_CONTEXT VARCHAR2(2500 char);

spring-batch-docs/asciidoc/schema-appendix.adoc

@@ -35,6 +35,16 @@ modified with additional indexes and constraints as desired. The file names are
 form `schema-\*.sql`, where "*" is the short name of the target database platform.
 The scripts are in the package `org.springframework.batch.core`.
 
+[[migrationDDLScripts]]
+==== Migration DDL Scripts
+
+Spring Batch provides migration DDL scripts that you need to execute when you upgrade versions.
+These scripts can be found in the Core Jar file under `org/springframework/batch/core/migration`.
+Migration scripts are organized into folders corresponding to version numbers in which they were introduced:
+
+* `2.2`: contains scripts needed if you are migrating from a version before `2.2` to version `2.2`
+* `4.1`: contains scripts needed if you are migrating from a version before `4.1` to version `4.1`
+
 [[metaDataVersion]]
 ==== Version