CICS Interview Questions
Customer Information Control System. To provide the control and services of the DB/DC system
The programming technique in which the task will not wait for the end-user replies on the terminal. Terminating the task every time the application needs a response from the user and specifying the next transaction to be started when the end user press any attention key (Enter, PF1 through PF24, PA1,PA2 and Clear) is pseudo-conversational processing.
Pseudo-conversational will start a new task for each input. By coding a CICS RETURN command specifying ‘TRANSID(itself). Conversational will have an active task during the duration of the data entry.
Multitasking is the feature supported by the operating system to execute more than one task simultaneously. Multithreading is the system environment where the tasks are sharing the same programs load module under the multitasking environment. It is a subset of multitasking since it concerns tasks which use the same program.
Reentrant program is a program which does not modify itself so that it can reenter to itself and continue processing after an interruption by the operating system which, during the interruption, executes other OS tasks including OS tasks of the same program. It is also called a "reenterable" program or"serially reusable" program.
A quasi-reentrant program is a reentrant program under the CICS environment. That is, the quasi-reentrant program is a CICS program which does not modify itself. That way it can reenter to itself and continue processing after an interruption by CICS which, during the interruption, executes other tasks including CICS tasks of the same program. In order to maintain the quasi-reentrancy, a CICS application program must follow the following convention:
Constants in Working Storage: The quasi-reentrant program defines only constants in its ordinary data area (e.g. working Storage Section ). These constants will never be modified and shared by the tasks.
Variable in Dynamic Working Storage: The quasi reentrant program acquires a unique storage area dynamically for each task by issuing the CICS macro equivalent GETMAIN. All variables will be placed in this DWS for each task. All counters would have to be initialized after the DWS has been acquired.
Restriction on Program Alteration: The program must not alter the program itself. If it alters a CICS macro or command, it must restore the alteration before the subsequent CICS macro or command.
A program is considered reentrant if more than one task can execute the code without interfering with the other tasks' execution.
There are times when many users are concurrently using the same program, this is what we call Multithreading.
A program or map loaded into the CICS nucleus so that it is kept permanently in main storage and not deleted when CICS goes “Short On Storage”.
TCP places data in TIOA and corresponding entry into TCT.
KCP acquires the transaction identifier from TIOA and verifies if it is present in PCT.
SCP acquires Storage in Task Control Area (TCA), in which KCP prepares control data for the task.
KCP then loads the application programs mentioned in PCT by looking for it in PPT.
If resident – real storage memory location is not present in the PPT the control is passed to PCP that loads the application programs from the physical storage location address given in PPT. The control is then passed to the application program (LOAD module).
By coding an EXEC CICS START in the application program
By coding the trans id and a trigger level on the DCT table
By coding the trans id in the EXEC CICS RETURN command
By associating an attention key with the Program Control Table
By embedding the TRANSID in the first four positions of a screen sent to the terminal.
By using the Program List Table
The CICS translator converts the EXEC CICS commands into call statements for a specific programming language. There are CICS translators for Assembler, COBOL, and PL/1.
Transaction routing is a CICS mode of intercommunication which allows a terminal connected to local CICS to execute another transaction owned by a remote CICS.
Function request shipping is one of the CICS modes of intercommunication which allows an application program in a local CICS to access resources owned by a remote CICS.
MRO is the mechanism by which different CICS address spaces within the same CPU can communicate and share resources.
A CICS task exists from the time the operator presses the enter key until the application program returns control to CICS.
A DB2 precompiler processes some SQL statements and converts others. It creates a data base request module (DBRM) for the binding step. The bind process uses the DBRM to create an application plan, which specifies the techniques DB2 will use to process the embedded SQL statements. The link/edit step includes an interface to the CICS/DB2 attachment facility.
The LOAD command retrieves an object program from disk and loads it into main storage - it's primarily used for a constant table that will be available system-wide.
When a program has been used in CICS at least once and then changed and recompiled.
Yes. Needs to be preprocessed.
DB2, DL/I, ORACLE
This occurs when a programmer Issues a Exec CICS Syncpoint command. this is called two phase because CICS will first commit changes to the resources under its control like VSAM files. and the DB2 changes are committed. Usually CICS signals Db2 to complete the next phase and release all the locks.
Yes in the DFHTST.
Destination Control Table used to define TDQs
The Program List Table records the set of applications programs that will be executed automatically at CICS start-up time.
The Transient Data Program(TDP).
PPT, PCT, (FCT, DCT, RCT (if needed)).
Register security information of all programs
PCT contains a list of valid transaction ID. Each transaction ID is paired with the name of the program ,CICS will load and execute when the transaction is invoked. On the other hand, PPT indicates each program's location which pertains to a storage address if the program has already been loaded or a disk location if the program hasn't been loaded. PPT will also be used to determine whether it will load a new copy of the program when the transaction is invoked.
BMS is Basic Map Support; it allows you to code assembler level programs to define screens.
A mapset is a collection of BMS maps link-edited together.
FIELD+L - Return the length of text entered (or for dymanic cursor positioning)
FIELD+F - Returns X(80) if data entered but erased.
FIELD+A - Used for attributes reading and setting
FIELD+I - Used for reading the text entered while receiving the map.
FIELD+O - Used for sending information on to the MAP.
MOVE –1 to FIELD+L field. Mention CURSOR option in the SEND command.
Mention FSET option in DFHMDF or set it dynamically in the program using FIELD+A attribute field.
The INTO option moves the information in the TIOA into the reserved specified area, while the SET option simply returns the address of the TIOA to the specified BLL cell or “address-of” a linkage-section
MDT ( Modified Data Tag ) is one bit of the attribute character. If it is off ( 0 ), it indicates that this field has not been modified by the terminal operator. If it is on ( 1 ), it indicates that this field has been modified by the operator. Only when MDT is on, will the data of the field be sent by the terminal hardware to the host computer ( i.e., to the application program, in end ). An effective use of MDT drastically reduces the amount of data traffic in the communication line, thereby improving performance significantly. Therefore, BMS maps and CICS application programs should be developed based on careful considerations for MDT.
Static positioning: Code the insert cursor (IC) in the DFHMDF BMS macro.
Relative positioning: Code the CURSOR option with a value relative to zero(position 1,1 is zero).
Symbolic positioning: Move high values or -1 to the field length in the symbolic map(and code CURSOR on the SEND command).
The Modified Data Tag can be set on:
1. When the user enters data into the field.
2. When the application program moves DFHBMFSE to the attribute character.
3. By defining it in the BMS macro definition.
The DFHMDF macro defines fields, literal, and characteristics of a field.
FSET specifies that the modified data tag should be turned on before the map is sent to the screen.
FRSET turns off the attribute byte; it's used to transmit only changed data from the terminal.
The Enter and PF keys transmit data from the screen; the PA keys tell CICS that a terminal action took place, but data is not transmitted.
MAPONLY is a SEND MAP operand that sends only fields with initial values to the screen. DATAONLY is the SEND MAP operand that specifies only data from the map area should be displayed.
STOPPER command will stop after completing its field , whereas AUTOSKIP command Will skip to next unprotected field after completing its field.
The map copybook and the load module.
Defines the display/transmission of field. most cases are an output field from the program.
Define EXTATT=YES and the correct terminal type.
Is the parameter to generate a symbolic map.
Brings the entire datastream from the terminal buffer.
The OUTRAGE condition will be set
DFHEIBLK is Execute Interface Block. It is placed in the linkage section automatically by CICS translator program. It must be the first entry in linkage section. CICS places values prior to giving control to the program and we can find almost any information about our transaction.
A logical message is a single unit of output created by SEND TEXT or SEND MAP commands. BMS collects the separate output from each command and treats them as one entity. This technique may be used to build CICS reports.
Only the symbolic map will be send
The physical mapset is a load module used to map the data to the screen at execution time. The symbolic map is the actual copybook member used in the program to reference the input and output fields on the screen.
An area used to transfer data between different programs or between subsequent executions of the same program. Needs to be defined in the Linkage Section.
CICS automatically provides some system-related information to each task in a form of EXEC Interface Block (EIB), which is unique to the CICS command level. We can use all the fields of EIB in our application programs right away.
The execute interface block lets the program communicate with the execute interface program, which processes CICS commands. It contains terminal id, time of day and response codes.
The cursor position in the map
Length of communication area
Current date and time
The EIBRCODE tells the application program if the last CICS command was executed successfully and, if not, why not.
TWASIZE=300 in PCT table.
When the length of the communication area (EIBCALEN) is equal to zeros, it means that no data was passed to the application.
We can also pass information in the following ways.
- By using a temporary storage queue
- By using an intrapartition TDQ
- By using the Task Work Area
- By using TCTUA
- Through a file
By defining it on the PCT (the Program Control Table)
The common systems area is the major CICS control block that contains system information, including pointers to most other CICS control blocks. The CSA points to all members of STATIC storage.
EIBAID is a key field in the execute interface block; it indicates which attention key the user pressed to initiate the task.
In COBOL storage was accessed via BLL cells using the SET option of ADDRESS commands. In COBOL II the special register, ADDRESS OF lets you reference the address of any Linkage Section field.
EIBRESP, EIBCALEN, EIBRRCDE, EIBTASK, EIBDATE, EIBTIME
The date and time at the task initiation
The length will be 0(zero).
An abnormal situation during execution of a CICS command is called an exceptional condition".There are various ways to handle these exception conditions:
1. Handle Condition Command: It is used to transfer control to the procedure label specified if the exceptional condition specified occurs.
2. Ignore Condition Command: It causes no action to be taken if the condition specified occurs in the program. That is control will be returned to the next instruction following the command which encountered the exceptional condition.
3. No Handle Option: This option can be specified in any CICS command and it will cause no action to be taken for any exceptional condition occurring during execution of this command.
4. RESP Option: This option can be specified in any CICS command. If the RESP option is specified in a command, CICS places a response code at a completion of the command. The application program can check this code, then proceed to the next processing.
No more than 16 in a single handle condition. If you need more, then you must code another HANDLE CONDITION command.
A HANDLE CONDITION command creates a “go-to” environment. An IGNORE command does not create a go-to environment; instead, it gives control back to the next sequential instruction following the command causing the condition. They are opposites.
No action is going to be taken for any exceptional conditional occurring during the execution of this command. The abnormal condition that occurred will be ignored even if an EXEC CICS HANDLE condition exists. It has the same effect as the EXEC CICS IGNORE condition except that it will not cancel the previous HANDLE CONDITION for any other command.
By coding an EXEC CICS POP HANDLE command.
Max. of 12 exceptional conditions can be given in a single HANDLE CONDITION.
CICS will take the default action specified for the condition
The ASKTIME command is used to request the current date and time. Whereas, the EIBTIME field have the value at the task initiation time.
CEDF : CICS-supplied Execution Diagnostic Facility transaction. It provides interactive program execution and debugging functions of a CICS programs.
CEMT : CICS-supplied Extended Master Terminal transaction. It displays or manipulates CICS control environment interactively.
CEBR : CICS-supplied Temporary Storage Browse transaction. It displays the content of Temporary Storage Queue ( TSQ ).
CECI : CICS-supplied Command Interpreter transaction. It verifies the syntax of a CICS command and executes the command.
We can able to determine if the application was started by (1) a transient data trigger level(QD), (2) a START command (S,SD), (3) user (U) or terminal input (TD), or (4) Distributed Program Link(D,DS).
SYNCPOINT without the ROLLBACK option makes all updates to protected resources permanent; with the ROLLBACK option it reverses all updates.
Transid is a transaction identifier, a four character code used to invoke a CICS task. CEMT is the master terminal transaction that lets you display and change the status of resources - it is the primary CICS service transaction.
Stop run will come out from the CICS region.
CICS automatically opens and closes files those are placed in FCT
Use a GETMAIN
If anyone want to restrict Trans-Id to single user, enter trans-id with ENQ. It won't allow any one else to use the same trans-id.
The following commands are available for the Program Control services:
LINK: To pass control to another program at the lower level, expecting to be returned.
XCTL: To pass control to another program at the same level, not expecting to be returned.
RETURN: To return to the next higher-level program or CICS.
LOAD: To load a program.
RELEASE: To release a program.
The XCTL command passes control to another program, but the resources requested by the first program may still be allocated. A task does not end until a RETURN statement is executed. While in LINK command, program control resumes its instruction following the LINK parameter. The disadvantage of LINK is that it requires that both the calling program and the called program remain in main memory even though both are no longer needed.
The next time the end user presses an attention key, CICS will start the transaction specified in the TRANSID option.
With a START or ATI.
In case of call , whenever you do changes to the called program you need to compile the calling program also. In case of link , it is not needed .
Issue the ENDBR command
Issue the READ command with UDTAE option.
Manipulate the record (DELETE or REWRITE command)
Issue START command
Issue two READNEXT commands (One for dummy skip)
Go to step two.
SET(ADDRESS OF LINKAGE-AREA
When we use INTO option with the READ command the data content of the record will be moved into the specified field defined in the Working Storage Section of the program. When we use SET option with the READ command , CICS sets the address pointer to the address of the record in the file input / output area within CICS, so that the application program can directly refer to the record without moving the record content into the Working Storage area defined in the program. Therefore, the SET option provides a better performance than the INTO option.
Yes, but not as part of the File Control Program. They are supported as extra partition transient data files.
Through the path. Define path as an FCT and use normal File control commands.
Define the file as recoverable. in cases where records have been inserted into the file, you may need to run a batch program to logically delete the inserted records.
MASSINSERT is a WRITE option that modifies normal VSAM split processing, leaving free space after the inserted record, so subsequent records can be inserted without splits. It is ended by an UNLOCK command.
First issue a STARTBR(start browse), which will position the browse at the desired record. Retrieve records by using subsequent READNEXT commands. Indicate the end of sequential processing with the ENDBR command. If the generic key is specified in the STARTBR command positioning in the file will be before the first record satisfying the generic key.For reading in descending order use the READPREV instead of READNEXT.
Temporary storage is either main or auxiliary storage that allows the program to save data between task invocations.
Transient data provides CICS programs with a simple method for sequential processing, often used to produce output for 3270 printers.
They are intrapartition, which can only be accessed from within CICS and extrapartition, which are typically used to collect data online, but process it in a batch environment.
INTRA-PARTITION Data queue.
In order to avoid confusion and to maintain data security, a strict naming convention for QID will be required in the installation. Moreover, for a terminal-dependent task (e.g., pseudo-conversational task), the terminal id should be included in QID in order to ensure the uniqueness of TSQ to the task.
Temporary Storage Queue names are dynamically defined in the application program, while TDQs must first be defined in the DCT (Destination Control Table). When a TDQ contains certain amount of records (Trigger level), a CICS transaction can be started automatically. This does not happen when using a TSQ. TDQ(extra partition) may be used by batch application; TSQ cannot be accessed in batch. The Transient Data Queue is actually a QSAM file. You may update an existing item in a TSQ. A record in a TDQ cannot be updated. Records in TSQ can be read randomly. The TDQ can be read only sequentially. Records in Temporary Storage can be read more than once, while records stored in Temporary Data Queues cannot. With TDQs it is “one read” only.
Temporary data stores.
Both are used to save data among tasks. but 1. COMMAREA is private to that transaction only . like every transaction has its own COMMAREA created by CICS as soon as the transaction is initiated . however TSQ , if queue id is known can be accessed by other transactions also 2. COMMAREA length is s9(4) comp i.e. 65k . but TSQ can have any length.3. COMMAREA is available only during the transaction is running. TSQ if created with auxiliary option resides in aux memory and available even if main memory crashes.4.normally COMMAREA is used to transfer data from one task to another while tsq is used widely within the task as a scratch pad.
Intrapartition TDQ is read destructive. extra partition tdq is not read destructive.
By specifying the ITEM option
An ASRA is the CICS interrupt code, the equivalent of an MVS abend code.
Any AEI_ indicates an execute interface program problem - the abending program encountered an exceptional condition that was not anticipated by the coding.
APCT - the program could not be found or is disabled.
ASRA – most common CICS abend, indicating a program check, identified by a one-byte code in the Program Status Word in the dump.
AKCP - the task was cancelled; it was suspended for a period longer than the transaction's defined deadlock timeout period.
AKCT - The task was cancelled because it was waiting too long for terminal input.
Any data exception problem SOC7, SOC4 etc.
DB2/IDMS not up
It occurs when program interruption takes place. e.g.: when alphanumeric string moved to numeric data item OR when arithmetic calculations performed on nonnumeric data item OR when an attempt made to read an occurrence of a table beyond the defined occurrences.
This is the error code for length, if length of the source data is more than the receiving field, This error will occur.