OSDOCS-19804:Update the z-stream RNs for 4.21.16

modules/zstream-4-21-16.adoc

@@ -0,0 +1,37 @@
+// Module included in the following assemblies:
+//
+// * release_notes/ocp-4-21-release-notes.adoc
+
+:_mod-docs-content-type: REFERENCE
+[id="zstream-4-21-16_{context}"]
+= RHSA-2026:17474 - {product-title} {product-version}.15 fixed issues advisory
+
+Issued: 13 May 2026
+
+[role="_abstract"]
+{product-title} release {product-version}.16 is now available. The list of fixed issues that are included in the update is documented in the link:https://access.redhat.com/errata/RHBA-2026:17474[RHBA-2026:17474] advisory. There are no RPM packages for this release.
+
+Space precluded documenting all of the container images for this release in the advisory.
+
+You can view the container images in this release by running the following command:
+
+[source,terminal]
+----
+$ oc adm release info 4.21.16 --pullspecs
+----
+
+[id="zstream-4-21-16-fixed-issues_{context}"]
+== Fixed issues
+
+* Before this update, when going into holdover a new data set was defined for `ts2phc` as it started reporting offsets, which did not meet the minimum number of samples. As a consequence, the PTP Operator  incorrectly reported a `FREERUN` clock state immediately. With this update, when going into holdover the offset is calculated based on the slope defined by the holdover thresholds. As a result, the offset steadily increases until it goes over the threshold. The clock state correctly transitions from `HOLDOVER` to `HOLDOVER OUT-OF-SPEC` and finally to `FREERUN`. (link:https://issues.redhat.com/browse/OCPBUGS-77473[OCPBUGS-77473])
+
+* Before this update, {ibm-cloud-title} was unable to process new `SecurityGroup` rule types such as `any` and older versions of the Software Development Kit (SDK) for the Virtual Private Cloud (VPC) could not unmarshal a VPC with these new types. As a consequence, the installation program could not set up a new VPC or use an existing VPC with the `any` protocol type. With this release, the SDK for the VPC has been updated to support the unmarshalling of the new types. As a result, the `SecurityGroup` rule bug is resolved and the installation program can create or use a VPC with the new `SecurityGroup` rule types. (link:https://redhat.atlassian.net/browse/OCPBUGS-84225[OCPBUGS-84225])
+
+* Before this update, a race condition in the container stop path caused panic during the second `StopContainer` call after the first call had been completed. As a consequence, a panic in the container stop path occurred during the race condition. With this release, a `stopDone `guard is added to the `WaitOnStopTimeout` parameter to fix the race condition. As a result, the container stop operation is more resilient, which reduces the likelihood of panics during concurrent `StopContainer` calls. (link:https://redhat.atlassian.net/browse/OCPBUGS-84922[OCPBUGS-84922])
+
+* Before this update, pagination controls were not present at mobile resolutions because PatternFly expected both top and bottom pagination controls to be used. With this release, pagination controls are present regardless of the mobile resolution. (link:https://redhat.atlassian.net/browse/OCPBUGS-84967[OCPBUGS-84967])
+
+[id="zstream-4-21-16-updating_{context}"]
+== Updating
+
+To update an {product-title} 4.21 cluster to this latest release, see xref:../updating/updating_a_cluster/updating-cluster-cli.adoc#updating-cluster-cli[Updating a cluster using the CLI].

release_notes/ocp-4-21-release-notes.adoc

@@ -44,6 +44,9 @@ include::modules/rn-ocp-release-notes-known-issues.adoc[leveloffset=+1]
 // Asynchronous errata updates
 include::modules/rn-async-errata.adoc[leveloffset=+1]
 
+// 4.21.16 RNs and updating
+include::modules/zstream-4-21-16.adoc[leveloffset=+2]
+
 // 4.21.15 RNs and updating
 include::modules/zstream-4-21-15.adoc[leveloffset=+2]