I have Solaris 9 on my server.
From SunSolve site, I see:

Solaris9 Sun Alert Patch Cluster (184.9 M)
&
Solaris9 (204.3 M)

What is the difference between the Sun Alert Patch Cluster and the "regular" patch cluster?

Thanks!

The Recommended Patch Cluster reflects the current version of all of the patches
required to address all Sun Alert issues. Some customers have adopted a policy of
periodically applying the current Recommended Patch Cluster to a system. While
this strategy does address all Sun Alert issues, it also introduces more change to
the system than is necessary. Similarly, reapplying the current Recommended
Patch Cluster on a scheduled basis is also not necessary.

The Sun Alert Pack reflects the lowest revision of all of the patches necessary to
address all Sun Alert issues, and the least possible change to your system while
still addressing all Sun Alert issues.