Chapter 2. Introducing SSA Loops
This chapter describes the principles of SSAloops, how SSA devices are known to the
system programs, and the rules that you must observe when you configure your SSA
loops.

Loops, Links, and Data Paths

In the simplest SSAconfiguration, SSA devices are connected through two or more
SSAlinks to an SSA adapter that is located in a using system. The devices, SSA links,
and SSAadapter are configured in loops. Each loop provides a data path that starts at
one connector of the SSAadapter and passes through a link (SSA cable) to the
devices. The loop continues through the devices, then returns through another link to a
second connector on the SSAadapter.
The maximum permitted length for an external copper cable that connects two SSA
nodes (for example, disk drives) is 25 meters (82 feet).
The maximum permitted length for an external fiber optic cable that connects two SSA
nodes (for example, disk drives) is 10 kilometers (32800 feet). Some devices, however,
can operate only at shorter distances. See your subsystem documentation for details.
Details of the rules for configuring SSAloops are given for each SSA adapter in Rules
for SSA Loopson page 22.
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