Bookshelf v7.8: About Midtier-Centric and Mainframe-Centric Upgrades

When upgrading your development environment, you can choose whether to perform a mainframe-centric or midtier-centric upgrade.

All Siebel upgrades on DB2 for z/OS are initiated from a midtier platform (Windows or UNIX) and the DDL and DML files necessary for the upgrade are generated on this platform. In all production environment upgrades, the DDL and the data migration DML files are transferred to the DB2 host where they are unpacked and applied; this process is guided on the mainframe using REXX panels. This is a mainframe-centric upgrade.

Historically, all development environment upgrades have been midtier-centric, that is, only the DDL upgrade files are run directly on the mainframe; all other upgrade steps are performed from the midtier and applied to the z/OS host using a Windows- or UNIX-based DB2 client. Midtier centric development upgrades are very similar to non-z/OS development upgrades.

Since the development environment upgrade was enhanced in Version 7.7.2, however, all development upgrade DDL (CREATE, DROP, DELETE, ALTER, and GRANT) and DML (INSERT, UPDATE, DELETE, and SELECT) can be executed on the mainframe host. Based on your business requirements, you can choose to perform either a midtier-centric or mainframe-centric development environment upgrade.

NOTE: By default, the Siebel software contains the midtier-centric development environment upgrade files. If you want to perform a mainframe-centric development environment upgrade, you need to copy and replace these files to generate the appropriate upgrade output files. See Generating Development Environment Mainframe-Centric Upgrade Files for further information.

Source and Target Databases

When performing a development environment upgrade from the midtier, the source database is upgraded in place. For recovery purposes, in-place upgrades are not supported for mainframe-centric development or production upgrades. Instead, a target database is built for the new release and data is unloaded from the existing source database and migrated in the appropriate format to the upgraded database. The source database is not upgraded, although minor modifications are made to it during the upgrade process. The source and target databases can be in different DB2 subsystems or in the same subsystem.

Upgrading a development environment from the midtier is a simpler, more automated process than performing a mainframe-centric development upgrade. However there are advantages and disadvantages to each type of upgrade, as shown in Table 7.

Table 7. Midtier-Centric and Mainframe-Centric Development Environment Upgrades
Upgrade	Advantage	Disadvantage
Midtier-centric development environment.	This type of upgrade follows previous Siebel upgrade flows and allows you to work with existing expertise. Requires less manual intervention and is a less complex procedure.	Does not allow you to take advantage of enhancements built into the mainframe-centric development environment upgrade. This upgrade is not easy to restart if failures occur so you must back up your database before upgrading. When running a job, your options are to: Stop on every error. Some SQL statements return acceptable errors so, if you select this option, you may have to manually remove statements already processed and rerun the job. Process complete file. If the complete file is processed and an unacceptable error is returned, it may be necessary to restore the database from backup and restart the upgrade.
Mainframe-centric development environment.	You can gain experience performing this type of upgrade that you can apply during your production environment upgrade. You submit SQL files in a JCL environment. If a job fails, you know immediately and can correct the problem and re-submit the job before data is corrupted. This process can be audited. Involves the use of familiar, native z/OS tools and utilities.	You require a TSO account and the correct access permissions and authority levels. Extra disk space is required because a source and target database are used in the upgrade. You must acquire the mainframe-centric development upgrade files and manually replace the related midtier-centric files.