vmcj/option/jit/sharedCodeCacheSize is a SAP Parameter attribute which is used to control shared code cache size for the VMC information. This is available within R/3 SAP systems depending on the version and release level.
Below is the standard documentation available and a few details of the attributes values .
The option specifies the size of the shared code cache. The shared code
cache contains compiled methods that are divided between all VMs.
See SAP Parameter Documentation for full SAP documentation for this profile parameter.