What do the return codes mean, when I install patches.

When you install patches, you see something like -
Installation of 'patch_number' failed. Return code X.

What does the X mean?

0 No error
1 Usage error
2 Attempt to apply a patch that's already been applied
3 Effective UID is not root
4 Attempt to save original files failed
5 pkgadd failed
6 Patch is obsoleted
7 Invalid package directory
8 Attempting to patch a package that is not installed
9 Cannot access /usr/sbin/pkgadd (client problem)
10 Package validation errors
11 Error adding patch to root template
12 Patch script terminated due to signal
13 Symbolic link included in patch
14 NOT USED
15 The prepatch script had a return code other than 0.
16 The postpatch script had a return code other than 0.
17 Mismatch of the -d option between a previous patch install and the current one.
18 Not enough space in the file systems that are targets of the patch.
19 $SOFTINFO/INST_RELEASE file not found
20 A direct instance patch was required but not found
21 The required patches have not been installed on the manager
22 A progressive instance patch was required but not found
23 A restricted patch is already applied to the package
24 An incompatible patch is applied
25 A required patch is not applied
26 The user specified backout data can't be found
27 The relative directory supplied can't be found
28 A pkginfo file is corrupt or missing
29 Bad patch ID format
30 Dryrun failure(s)
31 Path given for -C option is invalid
32 Must be running Solaris 2.6 or greater
33 Bad formatted patch file or patch file not found