There are 2 DB2 family databases. Each one needs different DBA skills.
Check the list of books for DB2 DBA for ZO/S
DB2 for ZO/s: Delivers large data capacity with high transaction performance. IBM DB2 for z/OS helps to reduce cost and complexity in IT infrastructure, simplify compliance, and leverage core asset — data , so you can transform and adapt while limiting risk and cost to achieve agility and efficiency by standardizing best practices. Gain unmatched availability, reliability, and security for business critical information .Even in the most favorable economic climate, businesses need to control costs and increase efficiency in order to improve their bottom line.
DB2 UDB: DB2 for LUW is also called UDB it runs on multi platforms. DB2 for Linux, UNIX and Windows is a database server product developed by IBM. Sometimes called DB2 LUW for brevity, it is part of the DB2 family of database products. DB2 LUW is the “Common Server” product member of the DB2 family, designed to run on most popular operating systems. By contrast, all other DB2 products are specific to a single platform.
The latest DB2 LUW release is version 10.5. DB2 LUW was initially called DB2 Universal Database (UDB), but over time IBM marketing started to use the same term for other database products, notably mainframe (z-Series) DB2. Thus the DB2 for Linux, UNIX and Windows moniker became necessary to distinguish the common server DB2 LUW product from single-platform DB2 products.
The current DB2 LUW product runs on multiple Linux and UNIX distributions, such as Red Hat Linux, SUSE Linux, AIX, HP/UX, and Solaris, and most Windows systems. Earlier versions also ran on OS/2.