Understand what is there in your Weblogic Server Startup Command

-Xms1536m -Xmx1536m	These represent the total heap (minus Perm space). Xms is the Initial Heap, set to 1.5Gb in this case. Xmx is Max Heap. It is good practice to set Xms = Xmx The max heap is limited by the RAM available on the server
-XX:NewSize=512m	This specifies the initial size of the Young generation,set to 512Mbin this example. It is better to set this as a percentage of the Heap using -XX:NewRatio
-XX:MaxNewSize=512m	This specifies the maximum size of the Young generation,set to 512Mbin this example. It is better to set this as a percentage of the Heap using -XX:MaxNewRatio
-XX:PermSize=64m -XX:MaxPermSize=128m	These values are the Minimum and Maximum sizes of the permanent generation heap space. Optimally, set PermSize equal to MaxPermSize to avoid heap having to be adjusted when permanent area grows. As specified earlier, this area of memory is over and above the Total Heap set using Xms
-XX:SurvivorRatio=8 -XX:TargetSurvivorRatio=90	The New generation area is divided into three sub-areas: Eden, and two survivor spaces that are equal in size. Use the -XX:SurvivorRatio=X option to configure the ratio of the Eden/survivor space size. In the above example, setting it to 8 means the ratio of Eden:SS1:SS2 is 8:1:1. So for a NewSize of 512 Mb, the two SS will be 51 Mb each, and Eden will be 512 MINUS (51 + 51) = 410 Mb. TargetSurvivorRatio of 90 allows 90% of the survivor spaces to be occupied instead of the default 50%, allowing better utilization of the survivor space memory.
-XX:MaxTenuringThreshold=10	This switch determines how many times the objects are hopped between the Survivor spaces before getting promoted to the older generation. The default value is 31.
-XX:+DisableExplicitGC
-XX:+PrintGCDetails -XX:+PrintGCTimeStamps -XX:+PrintTenuringDistribution -XX:+PrintGCApplicationConcurrentTime -XX:+PrintGCApplicationStoppedTime -Xloggc:/log/gc.log	These are GC specific settings asking for GC details and the log file name in which these details should be captured