Software collections or SCL - is a collection of 'add-on" software packages. Software Collections give you the power to build, install, and use multiple versions of software on the same system, without affecting system-side installed packages.
Redhat summarises the software collecitons as: "For certain applications, more recent versions of some software components are often needed in order to use their latest new features. Red Hat Software Collections is a Red Hat offering that provides a set of dynamic programming languages, database servers, and various related packages that are either more recent than their equivalent versions included in the base Red Hat Enterprise Linux system, or are available for this system for the first time."
To find out which collections are already installed, use the scl command:
$ scl --list devtoolset-3 devtoolset-8 httpd24 maven30 mysql55 rh-git29 rh-java-common rh-nodejs10 rh-php56 rh-python34 rh-python36
In order to use the package, you must first 'enable' its use and run a program with the package enabled. Bash starts a new shell with all variables set.
$ scl enable devtoolset-3 bash $ gcc --version gcc (GCC) 4.9.2 20150212 (Red Hat 4.9.2-6) Copyright (C) 2014 Free Software Foundation, Inc. This is free software; see the source for copying conditions. There is NO warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
Useful links:
https://www.softwarecollections.org/en/docs/guide/#sect-Enabling_the_Software_Collection