> why would you use old obsolete releases of mission critical software?
"If it ain't broke, don't fix it"
Because it's mission critical, and you can't afford for it to break. Once you hit a certain complexity, upgrades almost always break something:
APIs change. Undefined behavior changes. New bugs are introduced. A feature critical to your app starts performing worse. The above changes break something else you depend on (libraries, proxies, etc.)
Upgrading to a significantly changed version of a mission-critical app/library/language is a lot of work, and is sometimes impossible: many projects couldn't be reasonably ported to Python 3 if they wanted to; a lot of important libraries don't work on Python 3.
This is exactly why bug and security fixes are often backported into old versions. Python 2.5 is still receiving security patches. Apache 1.3 was maintained for years after 2.0 was considered stable.
Yes, especially with a database you can't just pull in new updates and expect them to work. It involves reading the release notes and doing a lot of testing. (much of it is automated)
Equally APIs are backwards compatible, behaviour is defined, bugs are fixed, performance is improved and software becomes more compatible with other software.
"If it ain't broke, don't fix it"
Because it's mission critical, and you can't afford for it to break. Once you hit a certain complexity, upgrades almost always break something:
APIs change. Undefined behavior changes. New bugs are introduced. A feature critical to your app starts performing worse. The above changes break something else you depend on (libraries, proxies, etc.)
Upgrading to a significantly changed version of a mission-critical app/library/language is a lot of work, and is sometimes impossible: many projects couldn't be reasonably ported to Python 3 if they wanted to; a lot of important libraries don't work on Python 3.
This is exactly why bug and security fixes are often backported into old versions. Python 2.5 is still receiving security patches. Apache 1.3 was maintained for years after 2.0 was considered stable.