resize tomcat heap

#before heap size

[root@localhost min]# jmap -heap 109487
Attaching to process ID 109487, please wait...
Debugger attached successfully.
Server compiler detected.
JVM version is 25.252-b09

using thread-local object allocation.
Parallel GC with 2 thread(s)

Heap Configuration:
   MinHeapFreeRatio         = 0
   MaxHeapFreeRatio         = 100
   MaxHeapSize              = 987758592 (942.0MB)
   NewSize                  = 20971520 (20.0MB)
   MaxNewSize               = 329252864 (314.0MB)
   OldSize                  = 41943040 (40.0MB)
   NewRatio                 = 2
   SurvivorRatio            = 8
   MetaspaceSize            = 21807104 (20.796875MB)
   CompressedClassSpaceSize = 1073741824 (1024.0MB)
   MaxMetaspaceSize         = 17592186044415 MB
   G1HeapRegionSize         = 0 (0.0MB)

Heap Usage:
PS Young Generation
Eden Space:
   capacity = 278921216 (266.0MB)
   used     = 22089864 (21.06653594970703MB)
   free     = 256831352 (244.93346405029297MB)
   7.919750357032719% used
From Space:
   capacity = 23592960 (22.5MB)
   used     = 17890904 (17.062095642089844MB)
   free     = 5702056 (5.437904357910156MB)
   75.83153618706598% used
To Space:
   capacity = 25165824 (24.0MB)
   used     = 0 (0.0MB)
   free     = 25165824 (24.0MB)
   0.0% used
PS Old Generation
   capacity = 51380224 (49.0MB)
   used     = 25454368 (24.275177001953125MB)
   free     = 25925856 (24.724822998046875MB)
   49.54117755500638% used

19498 interned Strings occupying 2433080 bytes.

#fix heap size

[root@localhost bin]# vi catalina.sh 
JAVA_OPTS="$JAVA_OPTS $JSSE_OPTS -Xms2048m -Xmx2048m"

[root@localhost bin]# ./startup.sh 
Using CATALINA_BASE:   /opt/tomcat/apache-tomcat-8.5.42
Using CATALINA_HOME:   /opt/tomcat/apache-tomcat-8.5.42
Using CATALINA_TMPDIR: /opt/tomcat/apache-tomcat-8.5.42/temp
Using JRE_HOME:        /usr
Using CLASSPATH:       /opt/tomcat/apache-tomcat-8.5.42/bin/bootstrap.jar:/opt/tomcat/apache-tomcat-8.5.42/bin/tomcat-juli.jar
Tomcat started.
[root@localhost bin]# ps -ef|grep tomcat
root     121692      1 99 21:55 pts/1    00:00:17 /usr/bin/java -Djava.util.logging.config.file=/opt/tomcat/apache-tomcat-8.5.42/conf/logging.properties -Djava.util.logging.manager=org.apache.juli.ClassLoaderLogManager -Djdk.tls.ephemeralDHKeySize=2048 -Xms2048m -Xmx2048m -Djava.protocol.handler.pkgs=org.apache.catalina.webresources -Dorg.apache.catalina.security.SecurityListener.UMASK=0027 -Dignore.endorsed.dirs= -classpath /opt/tomcat/apache-tomcat-8.5.42/bin/bootstrap.jar:/opt/tomcat/apache-tomcat-8.5.42/bin/tomcat-juli.jar -Dcatalina.base=/opt/tomcat/apache-tomcat-8.5.42 -Dcatalina.home=/opt/tomcat/apache-tomcat-8.5.42 -Djava.io.tmpdir=/opt/tomcat/apache-tomcat-8.5.42/temp org.apache.catalina.startup.Bootstrap start
root     121813 101213  0 21:55 pts/1    00:00:00 grep --color=auto tomcat
[root@localhost bin]# jmap -heap 121692
Attaching to process ID 121692, please wait...
Debugger attached successfully.
Server compiler detected.
JVM version is 25.252-b09

using thread-local object allocation.
Parallel GC with 2 thread(s)

Heap Configuration:
   MinHeapFreeRatio         = 0
   MaxHeapFreeRatio         = 100
   MaxHeapSize              = 2147483648 (2048.0MB)
   NewSize                  = 715653120 (682.5MB)
   MaxNewSize               = 715653120 (682.5MB)
   OldSize                  = 1431830528 (1365.5MB)
   NewRatio                 = 2
   SurvivorRatio            = 8
   MetaspaceSize            = 21807104 (20.796875MB)
   CompressedClassSpaceSize = 1073741824 (1024.0MB)
   MaxMetaspaceSize         = 17592186044415 MB
   G1HeapRegionSize         = 0 (0.0MB)

Heap Usage:
PS Young Generation
Eden Space:
   capacity = 537395200 (512.5MB)
   used     = 431985056 (411.9730529785156MB)
   free     = 105410144 (100.52694702148438MB)
   80.38498594702745% used
From Space:
   capacity = 89128960 (85.0MB)
   used     = 0 (0.0MB)
   free     = 89128960 (85.0MB)
   0.0% used
To Space:
   capacity = 89128960 (85.0MB)
   used     = 0 (0.0MB)
   free     = 89128960 (85.0MB)
   0.0% used
PS Old Generation
   capacity = 1431830528 (1365.5MB)
   used     = 22316296 (21.28247833251953MB)
   free     = 1409514232 (1344.2175216674805MB)
   1.558585011535667% used

20065 interned Strings occupying 2534056 bytes.
[root@localhost bin]# df -h
Filesystem               Size  Used Avail Use% Mounted on
/dev/mapper/centos-root   17G   16G  2.0G  89% /
devtmpfs                 1.9G     0  1.9G   0% /dev
tmpfs                    1.9G     0  1.9G   0% /dev/shm
tmpfs                    1.9G  195M  1.7G  11% /run
tmpfs                    1.9G     0  1.9G   0% /sys/fs/cgroup
/dev/xvda1              1014M  179M  836M  18% /boot
tmpfs                    377M   44K  377M   1% /run/user/1000
/dev/sr0                  67M   67M     0 100% /run/media/min/Citrix VM Tools
overlay                   17G   16G  2.0G  89% /var/lib/docker/overlay2/a1531f15d9370a70c0490f5b008a0ce775b75f45e6f7bc0c8f60230b3ea1c8c7/merged
shm                       64M     0   64M   0% /var/lib/docker/containers/5b970fbb9bf1967fed1bac5e6257f2a257b4fa817f8dac33586a86eb8fdc8d22/mounts/shm
tmpfs                    377M  4.0K  377M   1% /run/user/42
tmpfs                    377M   40K  377M   1% /run/user/0