difference between reentrant & Qusi reentrant

sivatechdrive · Posted: Thu Mar 03, 2005 11:48 am

Hi all

i have some doubt's in cics,plz respond

1. i know what is reentrant, but what is qusi reentrant

2. difference between reentrant and qusi reentrant

3. what is serial reusability

Thanks
Siva

ovreddy · Posted: Thu Mar 03, 2005 4:15 pm

Hi Siva,

"reentrant: The attribute of a program or routine that allows the same
copy of the program or routine to be used concurrently by two or more
tasks."

"quasi-reentrant: The attribute of a CICS application program by which
it is serially reusable between calls on CICS facilities."

Also, CICS COBOL 2 programs must be reentrant whereas CICS OS/VS COBOL must be quasi-reentrant.

In detail...

"Reentrant" that means that the execution of a program may be suspended and the operating system will decide that a different task is to execute the exact same code that was suspended. A reentrant program will allow this activity harmlessly for any number of "simultaneous" uses. In the case of a multiprocessor it may be that a second task executes the code on a second CPU while the first execution continues on the first CPU.

Quasi-reentrancy in CICS is not as strong a condition as reentrancy.
In quasi-reentrancy the possible suspension points are only at EXEC
CICSs. That means that the code segment executed between any two EXEC CICS (calls for CICS services) need only meet the lesser condition
known as serially reusable. Quasi-reentrancy need not worry about
multiprocessor considerations. Only one CICS task executes at a time.

In the case of the COBOL compiler you should use the RENT, RES and
NODYNAM options when compiling for CICS. You will get a load module
that meets all conditions needed for CICS. You may need to consider
the difference between reentrant and quasi-reentrant only if you write
your own code in a language that doesn't automatically accommodate
reentrancy (assembler language for example).

Bye,
Reddy.

meetsrk · New User Joined: 13 Jun 2004 Posts: 85

hi,

Reentrant and Quasi-reentrant are same.

Reentrant process under cics region is called Quasi-reentrant program.

Thru quasi-reentrant, we achieve puesdo conversation.

appasi · New User Joined: 12 Dec 2005 Posts: 20 Location: Bangalore

A program which does not alter itself
even if the program is suspended and restarted
any number of times is known as reentrant
program.

Any reentrant program running under CICS
region is called as Quasi-reentrant program.

kanak · Moderator Joined: 12 Mar 2005 Posts: 252 Location: India

1. A reentrant program is coded to allow one copy of itself to be used concurrently by several tasks: it does not modify itself while running.

2. A quasi-reentrant program is serially reusable by different tasks. When it relinquishes control, it must be in the same state as when it received control. Such a program can modify itself while running, and is therefore not fully reentrant