No shared spaces configured

Heap
garbage-first heap   total 6291456K, used 1368757K [0x0000000640000000, 0x00000007c0000000, 0x00000007c0000000)
  region size 2048K, 97 young (198656K), 9 survivors (18432K)
compacting perm gen  total 1048576K, used 230859K [0x00000007c0000000, 0x0000000800000000, 0x0000000800000000)
   the space 1048576K,  22% used [0x00000007c0000000, 0x00000007ce172e10, 0x00000007ce173000, 0x0000000800000000)
No shared spaces configured.

this was seen in a

java/jdk170_91-64b/bin/java -XX:-UseBiasedLocking -XX:SurvivorRatio=10 -verbose:gc -XX:+PrintGCTimeStamps -Xms6144m -Xmx6144m -XX:NewSize=256m -XX:MaxNewSize=256m -XX:PermSize=1024m -XX:MaxPermSize=1024m  -XX:+UseG1GC -XX:InitiatingHeapOccupancyPercent=60 

I am not really sure what this "No shared spaces configured" would mean - I could not find any decent documentation on this message. And it doesn't seem to be really an error message, nor something related to G1GC...

Referencing a WorkManager (ExecutorService) in a Web module or EJB module or at App level

at WAR level you can have a work-manager clause:
https://docs.oracle.com/cd/E24329_01/web.1211/e21049/weblogic_xml.htm#WBAPP627
but it's available also at EAR level:
https://docs.oracle.com/cd/E24329_01/web.1211/e24368/app_xml.htm#WLPRG487
http://xmlns.oracle.com/weblogic/weblogic-application/1.4/weblogic-application.xsd
and also at EJB level: https://docs.oracle.com/cd/E12840_01/wls/docs103/ejb/DDreference-ejb-jar.html

Useful links:
https://developer.ibm.com/answers/questions/168264/how-to-use-resources-defined-in-applicationxml-des.html
http://stackoverflow.com/questions/2887967/what-is-resource-ref-in-web-xml-used-for

Singleton Timer in WebLogic

If you have a JEE EJB Timer in a Cluster, maybe you want only 1 instance to be active. In this case you should implement a Cluster Aware Singleton Component :
https://blogs.oracle.com/muraliveligeti/entry/ejb_timer_ejb

- create table WEBLOGIC_TIMERS

configure a Datasource and set it in "cluster-Scheduling":