Use &CALL Without SUBSYS

If you are using &CALL without the SUBSYS facility, the following disadvantages are encountered:

An z/OS ATTACH is issued for each call. This means that the called program cannot easily remember things across calls.
Significant CPU time is expended in ATTACH processing
Continual opening and closing of files by z/OS
Use of either &LOCK (in NCL) or ENQ/DEQ (in assembler) to serialize