Under the Hood: Kubernetes QoS Classes

It is 3 a.m. and a node in your production cluster runs low on memory. When the dust settles, your payment service has been killed and restarted twice. The nightly batch job on the same node, the one nobody would miss for an hour, sailed through untouched. Nothing in the dashboards says why, and nobody made that choice on purpose. Except somebody did. Months earlier, someone wrote requests and limits into two manifests. The batch job got requests… Read More

Explained: SMF Records

A batch job ran overnight and consumed three times its usual CPU. A CICS transaction that normally completes in 12 milliseconds is suddenly taking 200. A user account was used to access a sensitive dataset at 3am. A DB2 tablespace is approaching its storage limit. None of these events sent an alert. Nobody was watching at the time. But every one of them left a record. Because on z/OS, almost everything that happens is written down. That writing-do… Read More

Explained: CICS Storage Management

It starts as a performance problem. Response times climb. Tasks start queuing. Then a message appears on the operator console: DFHSM0133 CICS is under stress (short on storage above 16MB) . New transactions are refused. The region grinds to a halt and has to be recycled. Short on storage is one of the most disruptive CICS failures in production, and unlike most failures it builds gradually. A storage leak in one transaction, a DSA limit set too co… Read More