Quiescing a Web server | Instructions for compatible upgrades
Compatible upgrades
We refer to upgrades as compatible if Web servers to which the updates have already been applied can be taken online while Web servers that have not yet been updated are still online. Without server affinity in the Load Balancer, this means that requests may be routed to updated and non-updated Web servers within the same user session.
Compatible upgrades that require a Web server to be offline while the update is being applied typically include:
- Hardware and capacity upgrades
- OS upgrades
- Software product upgrades
- Refresh packs, fix packs
- Fixes, APARs, iFixes, eFixes, and so on
If only compatible upgrades had to be performed, the Web server tier could be utilized over 50% at peak times, as there would only need to be enough capacity to compensate for one server being down at a time. However, this is usually not sufficient, as we discuss further in 27.2.3, Incompatible upgrades".
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