abap/objmgr/disable_gc is a SAP Parameter attribute which is used to control Object Manager: Disable Garbage Collection 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 .
For internal use by SAP Support only.
Deactivates the ABAP Objects Garbage Collector. When this happens,
objects can no longer be released. This is only advisable if a severe
error has occurred in the Object Manager and it is to be deactivated,
thus losing memory, until the next patch is available.
See SAP Parameter Documentation for full SAP documentation for this profile parameter.