Oracle to Sybase ASE Migration Guide

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ORACLE TO SYBASE ASE MIGRATION GUIDERev.1.3etc, and automatically convert the Oracle datatypes into their ASE equivalent, this is the fastest and most efficientschema migration method available.Section 4.2 describes how to use PowerDesigner for this purpose.Section 4.3 describes a possible approach to reverse-engineer the schema without PowerDesigner.4.2 Using Sybase PowerDesigner for database schema migrationSybase PowerDesigner is arguably the most advanced data modeling tool in the market. It is a stand-alone tool, runningon Windows. PowerDesigner supports over 30 database types, including Oracle and Sybase ASE.For more information on PowerDesigner, see http://www.sybase.com/powerdesigner .With PowerDesigner it is relatively straightforward to reverse-engineer most of the Oracle schema and convert it toSybase ASE. The central concept used by PowerDesigner is the PowerDesigner Physical Data Model (PDM). This is adatabase-independent model which can be converted to the SQL DDL dialect of each supported database.4.2.1 PowerDesigner schema conversion stepsFor detailed, step-by-step instructions on how to use PowerDesigner to convert the database schema from Oracle toSybase ASE, see the document “Migrating an Oracle Database to SAP Sybase ASE with PowerDesigner and ECDA (A Step-By-Step Practical Guide)” at http://www.sybase.com/support/techdocs/migration.Once the schema is reverse-engineered, run the completed DDL script in Sybase ASE and check for any errors.Note that some aspects of schema migration cannot be handled by PowerDesigner and will have to be handleddifferently. These aspects are described in section 4.4.4.3 Reverse-engineering the Oracle schema without Sybase PowerDesignerWithout using Sybase PowerDesigner, reverse-engineering the schema can be done in a number of ways:Use the Oracle SQL*Plus DESC command on all database objects, and process the output so that they arevalid DDL statements. This is likely to require significant manual script coding.Use the Oracle DBMS_METADATA package to extract DDL for the Oracle objects. This involves SQLstatements such as the following (for Oracle table 'MY_TABLE', in schema/user 'SALESAPP'). Note thatthese are only examples, this is not a complete list of all statement required to perform full reverse-engineering:SELECT DBMS_METADATA.GET_DDL('TABLE', 'MY_TABLE', 'SALESAPP') FROM DUAL;SELECT DBMS_METADATA.GET_DEPENDENT_DDL('INDEX', 'MY_TABLE', 'SALESAPP') FROMDUAL;SELECT DBMS_METADATA.GET_GRANTED_DDL('OBJECT_GRANT', 'SALESAPP') FROM DUAL;Use Oracle SQL Developer (a free Java-based tool, downloadable from oracle.com). This uses theDBMS_METADATA package (see previous bullet).Use TOAD (a low-cost tool, commonly used in many Oracle environments) to extract the object definitions,and then manually convert the Oracle datatypes into their ASE equivalent. This could be cumbersome whenlarge numbers of tables are involved.Once the Oracle schema has been reverse-engineered, the Oracle DDL needs to be converted to Sybase ASE syntax,including conversion from the Oracle datatypes to Sybase ASE datatypes. Section 4.7 describes the mapping fromOracle datatypes to Sybase ASE.In addition, some aspects of the Oracle schema require special attention; see section 4.4.4.4 Special cases in schema migrationThe following schema aspects require special attention:Database Schema Migration 18
ORACLE TO SYBASE ASE MIGRATION GUIDERev.1.3Oracle allows more columns per table than Sybase ASE (the limit depends on the ASE server's page size andon the table's lock scheme). If the limit in Sybase ASE is exceeded, an error will be raised when trying to createthe table. If this occurs, either the ASE server's page size will need to be increased, or the table needs to besplit vertically into multiple tables and all queries referencing the table likely have to be modified accordinglyIf the length of a column exceeds the maximum allowed length in Sybase ASE (the limit depends on the ASEserver's pagesize and on the table's lock scheme), such columns will have to be split into multiple columns andplaced in additional tables. All queries referencing the column likely have to be modified accordingly.PowerDesigner converts the Oracle BFILE datatype to the Sybase ASE image datatype. Since BFILE is adatatype used to store a locator (link) to an external binary file stored outside of the database, this is notfunctionally equivalent so application changes may be required. If a different ASE datatype is required, forexample, to hold the name of an externally stored file, change it manually.PowerDesigner 15.x cannot automatically convert the Oracle timestamp datatype to bigdatetime inASE, so this needs to be done manually. PowerDesigner 16.0 (release expected in August 2011) does not havethis limitation and will perform the conversion automatically. PowerDesigner 15.x cannot reverse-engineer Oracle users or security details (permissions). PowerDesigner 16.0(release expected in August 2011) does not have this limitation and is capable of handling these aspects.Since the SQL reserved words are different between Oracle and Sybase ASE, before attempting a databaseschema migration, all Oracle objects need to be checked against the Sybase ASE reserved words. Any Oracleidentifiers that are also Sybase ASE reserved words, need to be changed first. For a complete list of reservedwords in Sybase ASE, see “Adaptive Server Enterprise->Reference Manual: Building Blocks->Reserved Words”.Also see section 4.8 for queries that can be used to search for the occurrence of keywords in the Oracledatabase.The mapping of Oracle user-defined datatypes to ASE can be difficult and may require extensive manualintervention. The key to user-defined datatype migration is to fully understand the underlying base datatype.Note that user-defined datatypes can be nested. For Oracle, user-defined datatypes is an add-on option to thedatabase and is not widely used.4.5 Mapping the Oracle schema to Sybase ASE databasesSybase ASE does not have an identical interpretation of the concept of "schema" as the "Oracle schema". Whenmigrating an Oracle schema to Sybase ASE, there are two basic options to map the Oracle schema to Sybase ASE.For the sake of example, let's assume there are two Oracle users john and bill who own an Oracle schema, and eachschema has a table named salesdetails.The options are:Perhaps the most straightforward way to migrate, is to map each Oracle schema to a separate ASE database,where each database is owned ('dbo') by the corresponding user. This would result in two ASE databasesnamed john_db and bill_db (different names may of course be chosen), owned by ASE logins john andbill respectively; each database has table named salesdetails, owned by the dbo database user (the fulltable name would be dbo.salesdetails).However, this results in as many ASE databases as there are users owning an Oracle schema, of which theremight be many. While an ASE server can hold up to 32786 databases, it is highly impractical from a DBAperspective to have more than 20-50 databases.Map all Oracle schemas to a single ASE database with a multi-tenancy model. This means that the ASEdatabase user (which is linked to the ASE server login, which is the equivalent of an Oracle user) is used withinthe database to identify each object's owner. This will result in a more manageable ASE system since there willbe less ASE databases.In this case, the example would result in a single ASE database, let's say sales_db, in which ASE logins johnDatabase Schema Migration 19
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Oracle to Sybase ASE Migration Guide

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