When unified logging was introduced we aliased numerous Print/TraceXXX flags to turn on their UL counterpart. For example:

-XX:+PrintSharedSpaces is deprecated. Will use -Xlog:cds=info instead.

UL has been around long enough now that we can obsolete and then expire these aliases. The affected flags are:

  { "PrintSharedSpaces", LogLevel::Info, true, LOG_TAGS(cds) },
  { "TraceBiasedLocking", LogLevel::Info, true, LOG_TAGS(biasedlocking) },
  { "TraceClassLoading", LogLevel::Info, true, LOG_TAGS(class, load) },
  { "TraceClassLoadingPreorder", LogLevel::Debug, true, LOG_TAGS(class, preorder) },
  { "TraceClassPaths", LogLevel::Info, true, LOG_TAGS(class, path) },
  { "TraceClassResolution", LogLevel::Debug, true, LOG_TAGS(class, resolve) },
  { "TraceClassUnloading", LogLevel::Info, true, LOG_TAGS(class, unload) },
  { "TraceExceptions", LogLevel::Info, true, LOG_TAGS(exceptions) },
  { "TraceInvokeDynamic", LogLevel::Debug, true, LOG_TAGS(methodhandles, indy) },
  { "TraceLoaderConstraints", LogLevel::Info, true, LOG_TAGS(class, loader, constraints) },
  { "TraceMethodHandles", LogLevel::Info, true, LOG_TAGS(methodhandles) },
  { "TraceMonitorInflation", LogLevel::Trace, true, LOG_TAGS(monitorinflation) },
  { "TraceSafepointCleanupTime", LogLevel::Info, true, LOG_TAGS(safepoint, cleanup) },
  { "TraceJVMTIObjectTagging", LogLevel::Debug, true, LOG_TAGS(jvmti, objecttagging) },
  { "TraceRedefineClasses", LogLevel::Info, false, LOG_TAGS(redefine, class) },
  { "PrintJNIResolving", LogLevel::Debug, true, LOG_TAGS(jni, resolve) },

As noted in the source:

// NOTE: A compatibility request will be necessary for each alias to be removed.

We can continue to print what the equivalent -Xlog configuration is, but in-line with these flags being obsolete we will not set that Xlog configuration. (obsolete flags are ignored other than to produce a usage warning.)