Author: Robert Sample
Posted: Tue Mar 14, 2017 8:03 pm (GMT 5.5)
The z/OS 2.1 JCL User's Guide says on page 110
and on page 111:
_________________
TANSTAAFL
The first rule of code reuse is that the code needs to be worth re-using.
"We should forget about small efficiencies, say about 97% of the time: premature optimization is the root of all evil." -- Donald Knuth
Posted: Tue Mar 14, 2017 8:03 pm (GMT 5.5)
The z/OS 2.1 JCL User's Guide says on page 110
| Quote: |
| Exclusive control of a data set When a job has exclusive control of a data set, no other job can use that data set until completion of the last step in the job that refers to the data set except when downgrading ENQs. A job should have exclusive control of a data set in order to modify, add, or delete records. |
| Quote: |
| The job receives control of the data set if: v Another job is not using the data set. v Another job is using the data set but both the job requesting the data set and the job using the data set request shared control and no exclusive requests are pending. The job does not receive control of a data set if: v Another job is using the data set and that job has exclusive control. v Another job is using the data set, with either exclusive or shared control, and this job requests exclusive control. v Another job is using the data set, with shared control, and yet another, earlier job requests exclusive control. If a job requests data sets that are not available, the system issues the message âJOB jjj WAITING FOR DATA SETSâ to the operator. The job waits until the required data sets become available, unless the operator cancels the job. |
_________________
TANSTAAFL
The first rule of code reuse is that the code needs to be worth re-using.
"We should forget about small efficiencies, say about 97% of the time: premature optimization is the root of all evil." -- Donald Knuth