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There may be some other aspects to this.
I can see from the trace that the entry is not in the SCC.
When it tries to add it - it says "already exists in the cache"
1708168:16:40:14.185881133 0x000000002167d200 j9shr.1322 Entry >CM
findROMClass: for class org/springframework/boot/loader/launch/Launcher with classpath id 0
1708184:16:40:14.185956632 0x000000002167d200 j9shr.127 Entry
>RMI locateROMClass: Locate request for ROMClass org/springframework/boot/loader/launch/Launcher from helper ID 0 with cpeIndex -1
1708185:16:40:14.185958742 0x000000002167d200 j9shr.953 Entry >M
hllTableLookup: Entering lookup with name org/springframework/boot/loader/launch/Launcher
1708227:16:40:14.186051663 0x000000002167d200 j9shr.1327 Exit <CM
findROMClass: class org/springframework/boot/loader/launch/Launcher not found
...
then it is found
1709307:16:40:14.205634790 0x000000002167d200 j9shr.127 Entry >RMI
locateROMClass: Locate request for ROMClass org/springframework/boot/loader/launch/Launcher from helper ID 2 with cpeIndex 0
1709308:16:40:14.205636634 0x000000002167d200 j9shr.953 Entry >M
hllTableLookup: Entering lookup with name org/springframework/boot/loader/launch/Launcher
1709328:16:40:14.205688134 0x000000002167d200 j9shr.282 Entry >CMI touchForClassFiles:
Looking for class org/springframework/boot/loader/launch/Launcher in classpath 0x2004d7efa54. Searching up to index 0.
1709330:16:40:14.205691118 0x000000002167d200 j9shr.1293 Event
RMI locateROMClass: Locate succeeded. Returning 0x2004d7efa20. FoundAtIndex=0. StaleCPEI=0x0.
Locate request for ROMClass org/springframework/boot/loader/launch/Launcher from helper ID 2 with cpeIndex 0.
1709332:16:40:14.205694696 0x000000002167d200 j9shr.1525 Event CM commitMetaDataROMClassIfRequired : found duplicate class org/springframework/boot/loader/launch/Launcher in cache
1709333:16:40:14.205698962 0x000000002167d200 j9shr.1531 Event CM
commitMetaDataROMClassIfRequired :1709332:16:40:14.205694696 0x000000002167d200 j9shr.1525 Event CM commitMetaDataROMClassIfRequired : found duplicate class org/springframework/boot/loader/launch/Launcher in cache
1709333:16:40:14.205698962 0x000000002167d200 j9shr.1531 Event CM
commitMetaDataROMClassIfRequired : located an existing class, no store is required for J9ROMClass org/springframework/boot/loader/launch/Launcher at address 0x496d9880.
1709334:16:40:14.205702383 0x000000002167d200 j9shr.1532 Event CM commitMetaDataROMClassIfRequired : Nothing was stored in the cache for J9ROMClass org/springframework/boot/loader/launch/Launcher at address 0x496d9880
1709538:16:40:14.230017273 0x000000002167d200 omrport.657 Event J9
VM NLS message: Failed to store class org/springframework/boot/loader/launch/Launcher in shared cache for class-loader id 2
with URL /u/tmp/zowep/components/gateway/bin/gateway-service-lite.jar (index 0).
1709552:16:40:14.230254647 0x000000002167d200 j9shr.1496 Exit <API
j9shr_jclUpdateROMClassMetaData : exit after storing nothing in the cache for class org/springframework/boot/loader/launch/Launcherfor J9ROMClass org/springframework/boot/loader/launch/Launcher at address 0x496d9880.
1709334:16:40:14.205702383 0x000000002167d200 j9shr.1532 Event CM commitMetaDataROMClassIfRequired : Nothing was stored in the cache for J9ROMClass org/springframework/boot/loader/launch/Launcher at address 0x496d9880
1709538:16:40:14.230017273 0x000000002167d200 omrport.657 Event J9
VM NLS message: Failed to store class org/springframework/boot/loader/launch/Launcher in shared cache for class-loader id 2
with URL /u/tmp/zowep/components/gateway/bin/gateway-service-lite.jar (index 0).
1709552:16:40:14.230254647 0x000000002167d200 j9shr.1496 Exit <API
j9shr_jclUpdateROMClassMetaData : exit after storing nothing in the cache for class org/springframework/boot/loader/launch/Launcher
I did some measurements on the use of shared classes. and shower proper support would save > 60 seconds of startup time.
I took the classes which are not loaded into the shared classes cache, and loaded them myself, and stored them in the shared classes cache - and repeated it.
First time ( classes not in the cache )
"find" 8.89 seconds - 22021 requests
"load" 60.1 seconds - 10053 requests
"save in scc" 3.5 seconds 10053 requests
Second time - exploiting classes in the cache
find 11 seconds 22021 requests
Load 0.01 seconds 10 requests
save 0.01 seconds 10 request
time dropped from 72 seconds down to 11 - a saving of over 60 second
Currently one address space in Zowe starts in about 380 seconds... so this would reduce the startup time by 15%!
This is on my zPDT system on Linux.