Dynamic tables versus installation tables

As previously stated, JES2 may be extended through either the creation of a user table or a dynamic table. Which type of table to use for a specific extension depends on your needs. The following is a comparison of the advantages and disadvantages of each type.

User Table
- Only a single user table is allowed.
- The user table is linked to the table pair by one of the following:
  - The linkage editor, by naming the table USERxxxT and link-editing the table with the HASJES20 load module.
  - An installation exit (such as exit 0), which stores the address of the table in the field MCTxxxTU.
- The user table overrides the JES2 table and all dynamic tables.
Dynamic Table
- An unlimited number of dynamic tables may be provided.
- The dynamic table is linked to the table pair automatically when the load module containing it is loaded through the LOAD(xxxxxxxx) initialization statement.
- The dynamic table overrides the JES2 table but may be overridden by the user table.

IBM® suggests that vendor products use dynamic tables for the following reasons:

Your installation is not required to take any extra action to include the tables, such as merging them with your own or other vendors' tables.
The dynamic tables can be easily overridden by a user table.

You can use either dynamic or user tables if you code your own tables. If you want to create separate sets of tables for different functions, you can use dynamic tables. If you want to override a dynamic table provided by a vendor, you can use a user table.