When control returns to the caller, the GPRs contain:
- Register
- Contents
- 0
- Unchanged
- 1
- Used by the system
- 2-13
- Unchanged
- 14
- Used by the system (LINKAGE=BRANCH) or unchanged (LINKAGE=SVC)
- 15
- Return code
When control returns to the caller, the ARs contain:
- Register
- Contents
- 0-15
- Unchanged
Some callers depend on register contents remaining the same before
and after issuing a service. If the system changes the contents of
registers on which the caller depends, the caller must save them before
issuing the service, and restore them after the system returns control.