Four were entries to datasets that did not exist. Looking at CICS usage statistics for a six-week period, another weren't used, so our target list was smaller. These statistics also showed that some of these files were not updated within CICS. So, they didn't need to be converted to RLS, further reducing our list.
Our client also had some ESDS datasets, we talk more about these below. From this list, we created 'blocks' of datasets to be converted. We chose the lesser used datasets and less important datasets first, moving towards the highest used.
We also researched what the applications did with these files. We found programs that opened and closed files within CICS.
We found others that changed attributes of the files between read-only and update. We found programs that inquired on the status of each file, and this affected processing. More on this in a moment. We also looked at applications accessing our VSAM datasets remotely via function shipping, and determined if they also needed to convert their definitions to RLS. We looked at backups, and any issues that may cause us problems. We also found that some batch jobs were opening and closing VSAM files.
We talk about what we found here in the third article in this series. We were also concerned about performance. And with good reason: performance will be degraded as users always try to get a lock for the 'next' empty record.
Our client had a few ESDS files. We defined two DFSMS storage classes: one for normal use, and one used for files that were backed up using snapshot technology. All RLS storage classes shared coupling facility cache and lock structures. We considered using extended addressing for all files. However, we had programs that used the RBA address. These would continue to work until a doubleword was required for the RBA. We decided that we wanted notice of this an abend , rather than just letting our programs use the wrong RBA without notice.
We had a few CICS programs that would change file attributes. For example, files would periodically be disabled for batch processing, and then re-enabled. We spent a lot of time ensuring application knew what they were doing.
We had a similar issue in batch: batch jobs would close CICS files to do processing. Regards, Jack. Flushing a file buffer in awk. Flush the CICS file buffer. We are having trouble with debugging an application. It would be very helpful if we could make the record write to the file directly. It seems that the record stays in the buffer for hours before we can see it in the file.
Of course closing and reopening the file works, but that forces everyone to stop testing. Is there a way to force - flush - refresh the data directly to the file? Thanks Mary.
Bill Quote:. Hey, Mary. Board index » cobol All times are UTC. Page 1 of 1. These days, users want information within seconds and in real time. To provide such quick service, we need a system which can process information online. CICS allows users to communicate with the back-end system to get the desired information. Examples of online programs include online banking system, flight reservation, etc. Although, multiple users are working on CICS system but it gives a feel to user that he is the single user only.
CICS is an operating system in itself, as it manages its own processor storage, has its own task manager which handles execution of multiple programs, and provides its own file management functions.
CICS provides online environment in batch operating system. Jobs submitted are executed immediately. CICS itself acts as an operating system. Its job is to provide an environment for online execution of application programs. CICS runs in one region or partition or address space. CICS handles scheduling for programs running under it. There are five major services which are provided by CICS. All these services together perform a task. It takes care of the status of all CICS tasks.
This is called multitasking. CICS tries to prioritize the response time to the most important task. As soon as a task begins, it becomes necessary to associate the task with the appropriate application program. Although many tasks may need to use the same application program, CICS loads only one copy of the code into memory. Each task threads its way through this code independently, so many users can all be running transactions that are concurrently using the same physical copy of an application program.
Storage control acquires, controls, and frees dynamic storage. CICS facilitates servicing of data handling requests from application programs. CICS provides application programmers a set of commands for dealing with data set and database access and related operations. CICS facilitates management of data integrity by control of simultaneous record updates, protection of data as task ABENDs and protection of data at system failures.
Application Programming Services interface with application programs. We will be discussing more in detail in upcoming modules. It provides series of statistical information that can be used for system tuning. We must have knowledge of the basic terms used in CICS to get a better understanding of how it works. Application programs use CICS for communication with remote and local terminals and subsystems.
The Information Display System is a family of display and printer terminals. Today, emulation software is available which means that even normal PCs can be used as terminals. All processing needs to be done by the application program. The CRT monitor displays the output or the input fields of the application program. A screenshot of a Model of CRT monitor is shown below. The display characteristics like intensity, protected, non-protected of the field can be set using BMS which we will be discussing in detail in upcoming modules.
When the user types text or numbers using non-aid keys, CICS will not even know if the user is typing anything or not.
A CICS program is invoked through a transaction. A CICS transaction is a collection of logically related programs in an application. The whole application could be logically divided into several transactions. Transaction identifiers which are 1 to 4 characters long are used to identify the transactions which the users want to do. A programmer links one program to the transaction identifier which is used to invoke all the application programs for that particular transaction.
Users invoke an application by using one of the transaction identifiers. CICS looks up for the transaction identifier to find out which program to invoke first to do the work requested.
It creates a task to do the work, and transfers control to the mentioned program. A task can receive data from and send data to the terminal that started it. It can read and write files and can start other tasks also. The difference between a transaction and a task is that several users can invoke a transaction but each user initiates his own task. LUW states that a piece of work should be done completely or not done at all. We will discuss more about it in upcoming modules.
An application is a series of logically grouped programs to form several transactions which is used to complete a specific task for the end-user. The five CICS system components described earlier are a convenient grouping of CICS system programs, each of which performs its own specialized functions. CICS nucleus is constructed by the control programs and corresponding control tables.
It provides unique advantages. It makes the CICS system highly flexible and thus easy to maintain. It transfers the control between programs and in the end, it returns the control back to the CICS. FCP is used to provide application programs with services like read, insert, update or delete records in a file.
It keeps exclusive control over the records in order to maintain data integrity during record updates. It is used to control allocation and deallocation of storage within a CICS region. These tables need to be updated accordingly with the application information for successful execution of CICS application programs. Terminal Control Program along with terminal control table recognize the incoming data from the terminal.
It checks if the program is loaded or not. If it is loaded, then the task use counter is increased by 1. If the program is not loaded, then the program is first loaded and the task use counter is set to 1. It gets the load library address from the PPT table. If it finds one, then it checks in the PPT table to find the location of the Program to execute it.
If the program is already available in the memory, it starts executing that particular program; if not, it loads the program to the memory from the secondary storage and then starts executing it.
The terminal operator initiates the transaction by typing a 1 to 4 character transaction-id and pressing the ENTER key. The TCP periodically checks all the terminals for input. It is used to inquire and update the status of CICS environments and also for other system operations. One can overwrite the status of the file displayed to change it. CECI is used to check the syntax of the command.
It executes the command, only if the syntax is correct. It gives you the list of options available. Following example shows how to send mapped output data to terminal.
We will be discussing about MAPS in the upcoming modules. It is used for debugging the program step by step, which helps in finding the errors. The terminal is in EDF mode message will be displayed. Now type the transaction id and press the enter key. After initiation, with each enter key, a line is executed. Before executing any CICS command, it shows the screen in which we can modify the values before proceeding further. It is used to display contents of a temporary storage queue or TSQ.
CEBR is used while debugging to check if the items of the queue are being written and retrieved properly. We will discuss more about TSQ in the upcoming modules. Each command could be achieved by executing a series of CICS macros. This feature of operating system allows more than one task to be executed concurrently. The task may be sharing the same program or using different programs. The CICS schedules the task in its own region. This feature of the operating system allows more than one task to be executed concurrently sharing the same program.
For multi-threading to be possible, an application program should be a re-entrant program under the operating system or a quasi-reentrant under the CICS. A re-entrant program is one which does not modify itself and can re-enter in itself and continue processing after an interruption by the operating system.
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