The problem here is, that for SHAREOPT(4,4), the extending of VSAM size will fail because of DISP=SHR. This is from documentation of VSAM. It has to do with the buffers and control area splits. However for SHAREOPT(4,3) it doesn't have this problem because of the CBUF which eliminates the restriction of control area splits.
You need to modify all your JCL to include the DD parameter RLS=CR
"You can install the TDF database on SMS-managed DASD, and activate RLS by adding the RLS parameter to each of the DD statements of the data sets that make up the TDF database. If this option is used, the RLS parameter must be either CR or CRE."
The parameters are shop specific, with regards to response time, and data integrity.
RLS=CR, Consistent Read; the application will put a share lock on
the record while reading and will not read records that are held
for update by another user.
RLS=CRE, Consistent Read Explicit; the application will hold a record it
it is reading until is issues a commit point. CRE only works with
applications that log updates and use commits to manage
transaction back out.
//DDNAME DD DSN=dataset.name, DISP=SHR,RLS=CR