According to Red Hat's website, you should be able to demonstrate knowledge in...

Installing and configuring a Red Hat Network Satellite server

Configuring users, groups, administrators, and activation keys on a Satellite

Creating base and child channels on a Satellite

Using Cobbler and Satellite to install, configure, and manage systems

Managing data using logical volumes and snapshots

Configuring high-availability clusters using physical or virtual systems

Configuring a GFS file system to meet performance, size, and quota objectives

Configuring iSCSI targets and initiators

Configuring a Kerberos realm

Configuring Red Hat Directory Server to provide a centralized directory with access control

Configuring Red Hat Enterprise Linux® clients to authenticate using various mechanisms, including Kerberos, LDAP, and Microsoft Active Directory

Configuring and managing hypervisors and virtual hosts using Red Hat Enterprise Virtualization

Analyzing system performance and behavior using tools such as vmstat, iostat, mpstat, and sar

Configuring systems to provide information using SNMP

Configuring runtime kernel parameters

Analyzing system and application behavior using ps, strace, top, Oprofile, and Valgrind

Configuring disk subsystems and scheduling algorithms and network buffers for optimal performance for specific requirements

Also according to Red Hat, aside from knowledge, you must also be RHCE, which requires RHCSA. If you have RHCE, you must pass the following in order to take the RHCA test...
Red Hat Enterprise Security: Network Services Expertise Exam (EX333)

Red Hat Enterprise Deployment and Systems Management Expertise Exam (EX401)

Red Hat Enterprise Clustering and Storage Management Expertise Exam (EX436)

Red Hat Enterprise System Monitoring and Performance Tuning Expertise Exam (EX442)

Red Hat Enterprise Directory Services and Authentication Expertise Exam (EX423)
or Red Hat Enterprise Virtualization (RHCVA) Exam (EX318)