CL Interview Questions

Q: How we define Data area that will specify a default date format of *YMD, and a default date separator / 

By defining CRTDTAARA keyword,  we can create data area. Below is the command for data-area with default data format *YMD  and default Separator/ .

CRTDTAARA DTAARA(MYLIB/RPGLEHSPEC)

          TYPE(*CHAR)

          LEN(80)

          VALUE('datfmt(*ymd) datedit(*ymd/)')

Q: How we will check whether job is batch or interactive?

RTVJOBA PARM (&JOBTYPE)

&JOBTYPE is a 1-character field that contains '0' (zero) means batch or '1' refers to an interactive job.

Q: How can we run a Batch Job?

SBMJOB Command.

Q: Is PGM keyword mandatory?

PGM keyword is an Optional. It becomes mandatory when we need to pass parameter to the CL program.

Q: Use of OVRDBF command with syntax?

Override with Database File (OVRDBF) command is used to

·         Replace the file name in the program.

·         Override certain parameters of a file that are used by the program.

Syntax:

OVRDBF FILE (overridden-filename) TOFILE (new-filename) MBR (member-name)

Q: What is an OPNQRYF in CL

·         OPNQRYF command creates a temporary file access path and will discard the access path after its use.

·         It can be used to sort records in order, selecting a subset of available records, grouping records or joining records.

Q: How we can update the records in CL?

·         we cannot update the records in CL.

·         we can do it by RUNSQLSTMT (update).

Q: How we can find out the job name and other job details in CL?

We can find the job name and other job details by using the RTVJOBA (Retrieve Job Attributes) command.

Q: Why would the PGM line contain a PARM?

PARM is used to pass parameters.

Q: How we read multiple files in CL?

By using OPNID we can read multiple files in the CL program.

EX:

DCLF    FILE(LIBNAME/FILENAME1) OPNID(FILE1)

DCLF    FILE(LIBNAME/FILENAME2) OPNID(FILE2)

Q: What does CL stands for in AS400?

CL stands for Control Language, which is used to call system functions and control operations.

Q: Maximum no of parameter passed in a CL?

255.

Q: What is the difference between the DOU and DOW operation codes?

DOW – Checks the condition before executing the loop

DOU - Checks the condition After executing the loop

Q: How we declare variables and files in CL?

DCL, DCLF

EX:

DCL VAR(&VARIABLE1) TYPE(*CHAR) LEN(8) 

DCLF FILE(FILENAME1) RCDFMT(*ALL)

Q: What are the data types available in CL?

*CHAR-Contains character string value

 *DEC -Contains decimal value

 *LGL- Contains '1'/ '0'

Q: If the field is defined in DDS, how is it referenced in a CL program?

DCL        VAR(&VARNAME)

Q: What are the CL commands used to process the files, variables used in the program.?

OVRDBF, CHGVAR, SNDPGMMSG

Q: What are logical control commands used in CL?

IF, THEN, ELSE, DO, ENDDO, DOWHILE, DOUNTIL, DOFOR, LEAVE, ITERATE, GOTO, WHEN, OTHERWISE, ENDSUBR.

Q: Can you add a record to file thru CL?

NO

Q: How do we change the value of a particular variable in CL?

By using CHGVAR keyword.

EX: CHGVAR VAR(&VARIABLENAME) VALUE('VALUE')

Q: Define ITER / LEAVE?

·         ITER:    Transfer the control before do loop. 

·         LEAVE: Transfer the control after do loop.

Q: What are the statements, which is not used in CLLE that is used in CLP?

·         RCLRSC which is replaced by RCLACTGRP

·         TFRCTL

Q: CL processing commands & program control commands?

PROCESSING commands are CHGVAR, SNDPGMMSG, OVRDBF, AND DLTF.

PROGRAM CONTROL commands are CALL, RETURN, TFRCTL

Q: Define indicator in CL?

We can set on or setoff the indicator by the command.

·         CHGVAR (&IN40) VALUE (‘0’) ->setoff

·         CHGVAR (&IN40) VALUE (‘1’) -> seton

Q: What is QCMDEXC command in CL how it helps?

·                 QCMDEXC is an API to Execute Command.

·                 This API used to run a command from within a high-level language.

·                 After the command runs, control returns to your High-level language program.

Q: What are the various stages for a job after it is submitted?

Job queue, Active job, an OUTQ is the three stages after the job has been submitted.

Q: How to see active jobs of the system.

Using WRKACTJOB command

Q: How to see the CPU usage?

WRKACTJOB or WRKSYSSTS

Q: What is JOBQ and PRINTQ?

·         Jobs go into the job queue in order to run in a subsystem.

·         Print queue where the printer files (report) reside and wait for their turn to get printed.

Q: Built in function in CL?

·         %SUBSTRING or %SST

The built-in sub-string function generates a character string which is a subset of an existing character string and can only be used with a CL program.

%SUBSTRING (Character-variable-name Starting-position length)

Or

%SST (Character-variable-name Starting-position length)

·         %SWITCH

Q: What is PWRDWNSYS?

The PWRDWNSYS command used Power down, which prompts the system to issue ENDJOB * IMMED for all system operations, followed by System Termination.

Q: String operation in CL?

*CAT ->Concatenate without editing.

*BCAT-> Trailing blanks are truncated in first string. One blank is inserted, and the second string is then concatenated. The second operand lead blanks are not truncated.

*TCAT->All trailing blanks are truncated in the first string, and the second string is concatenated afterwards. Any Second Operand leading blanks are not truncated.

Q: What is the difference between CALL and Transfer Control (TFRCTL)?

CALL	TFRCTL
Call transfers the control as per CALL STACK	Transfer Control (TFRCTL) will disable the CALL STACK and transfer the control to the calling program.
The CALL is used to different types of programs. Ex: RPGILE/400,CL/400,C/400,COBOL/400.	TFRCTL is used only in the CL programs.

Q: What is DSPMSGD?

Display’s all messages in message file with its basic message description.

Q: What CL command is used to read a file?

RCVF - Receive File

Q: How can you read a file in CL?

·         We can read a file by using RCVF command.

·  To read all the records until we reach EOF, we should use RCVF followed by MONMSG command with MSGID (CPF0864) followed by GOTO command label to branch and prior to RCVF command.

Q: What CL command is used to determine the logical files associated with a physical file?

DSPDBR (Display Database Relations)

Q: How can you set lower limit to a file in CL?

·         POSDBF set to '*Start' with 'File Position' parameter.

·         OVRDBF which enables the file to be set to Key Value, RRN or * START

Q: Which CL command to write file?

SNDF - Send File

Q: Which CL command is equivalent to write/read a display file in RPG?

SNDRCVF - Send/Receive File

Q: How we can share access path?

To share the access path we create an open data path in our CL program with OPNQRYF command and later we share this ODP with the called RPG program.

OVRDBF  FILE (FILENAME1) TOFILE (LIB/ PF) SHARE (*Yes)

OPNQRYF    FILE(libname/filename                                       +

Member-name                                                    +

Record-format-name)                                         +

OPTION(open-option)                                        +

FORMAT(lib name/database file name              +

Record-format name)                                         +

QRYSLT(query selection)                                  +

KEYFLD(field name)

Q: Difference between logical file and OPNQRY?

·         The main difference between logical file and OPNQRY is that a logical file is a permanent entity and OPNQRYF is not.

·         Any time we use the same sort order it is safe to use LF.  If we need multiple sorting orders / random scanning, then OPNQRY will go.

Q: How will you plan the procedure for a method of delivering regular, high volume checks that only needs to pick records that are flagged for processing?

With the help of OPNQRYF command, we can select the records from database file.  

Steps involved:

1.   OVRDBF with SHARE (*YES)

2.    OPNQRYF

3.    CALL the program

4.    DLTOVR

5.    CLOF

Q: what does Return command do in CL?

The Return command (RETURN) returns control in call stack to the next higher call stack entry.

Q: How we retrieve data area in CL?

The command RTVDTAARA is used to retrieve the data area and store the value in a CL Variable.

Syntax:

RTVDTAARA   DTAARA(DATAAREANAME) RTNVAR(&CLVAR1)

Q: How we can find out, how many records in a file through CL.

The command Retrieve Job Attributes (RTVJOBA) is used to figure out how many records a file holds.

Example to retrieve the message queue name and library name

RTVJOBA SBMMSGQ(&MSGQ) SBMMSGQLIB(&MSGQLIB)

Q: Command to retrieve a specific member in a file?

The command RTVMBRD retrieves a specific member 's description.

Q: How we retrieve system date in CL?

We can get values like date, time, month, year, day, century using RTVSYSVAL Command.

Q: How can you schedule a job to run on a regular basis?

We need to create a job scheduler to run a job on a regular basis. We can create a job scheduler using the ADDJOBSCDE command. We can list all job schedulers running by using the WRKJOBSCDE command, and we can delete a job scheduler by using the RMVJOBSCDE command, or we can delete a job scheduler by using the RMVJOBSCDE command. We can reschedule the job by using CHGJOBSCDE.

Q: How can you check the date in CL?

By using command CVTDAT.

Q: What is command to convert date format in CL?

CVTDAT

Q: What is command to Write or update to a database file in CL?

No such command exists in CL to write / update in CL database File.

Q: What is the command used for retrieving user profile attributes?

RTVUSRPRF

Q: What is data area and different types of data areas in CL?

·         Data area used to store the shared data of different jobs running on the system.

·         It is generated/created by using the command CRTDTAARA.

Q: Different types of data areas in CL?

Types of data area:

1)    User defined data area

2)    System defined data area

·         Local data area (LDA)

·         Group data area (GDA)

·         Program initialization parameter (PIP) data area.

Q: What type and length of LDA is?

*CHAR, 1024 bytes

Q: What is GDA?

The system creates a GDA when group jobs become an interactive job. For group only one GDA may exist.

Q: Command to create the data area?

CRTDTATARA

Q: How do you access the local data area in a CL program?

RTVDTAARA DTAARA (*LDA) RTNVAR (&VAR)

Q: What are the various steps involved in accessing Data Area in CL?

·         RTVDTAARA    Retrieve data area

·         CHGDTAARA   Edit data area

·         DSPDTAARA    To view/ display data area

Q: What is a Message and types of messages?

Message is information communicated among users, programs, and workstation. 2 types of messages:

1)      Impromptu/Immediate message

2)      Predefined message

Q: How can a programmer send a message from a CL program?

Using SNDPGMMSG (Send Program Message) command

Q: What is a Message Queue?

·         Message queues can be used to send & receive messages.

·         We store messages received by user, system or workstation in the storage pool and take the appropriate action according to the message and send them back to the user / application / workstation.

Q: What are different Types of message queues?

Different types of message queues:

·         Workstation message queue

·         User profile message queue

·         Job message queue

·         System operator message queue

·         History log message queue

Q: Explain QSNDDTAQ and QRCVDTAQ?

QSNDDTAQ

•         By using this command we can send data same / another program.

•         QSNDDTAQ    PARM (QUEUENAME LIB  &LEN  &DAT)

QRCVDTAQ

•         By using this command  we can receive data same /another program

•         QRCVDTAQ    PARM(QUEUENAME LIB &LEN &DAT &WAIT)

 Q: What are the mandatory parameters for declaring a Data queue?

•         QUEUE NAME

•         LIB NAME

•         LENGTH

•         DATA

•         WAIT

Q: How we trap error/exception handling in CL?

MONMSG command.

Q: What is the MSGID to know the EOF (end-of-file)?

CPF0864

Q: Specify levels of MONMSG Command?

Two levels of MONMSG Command.

1.    Program level: The MONMSG is specified in CL program immediately following the last declared command.

2.    Specific command level: We will write the MONMSG command immediately and a CL command follows.

Q: MSGID to catch all generic messages ins CL?

MONMSG    MSGID (CPF0000)

Q: What's a Output queue ( *OUTQ?)

An area, which stores all spooled files waiting to be printed.

Q: What's a Job queue (* JOBQ?)

An area that stores all jobs waiting to be compiled.

Q: Explain parameter passing.

To pass variables from a CL or RPG program to another program.

Q: How can programmer exit out of CL program?

RETURN command.

Q: Can we perform any action on trapped MONMSG? Explain with an example.

Yes, we can perform an action on the trapped error messages

Ex: Whenever we receive an MSGID CPF9801, we are redirecting to ERROR command Label to execute.

MONMSG     MSGID(CPF9801) EXEC (GOTO CMDLBL(ERROR))

Q: How we get to know check object is failed, what is the MONMSG ID.

The command Check Object (CHKOBJ) used to check the existence of an object and verifies the authority of the user for the object before attempting to access it. If the object appears and the user does not have the correct authorization for the object, the user is given error messages.

CPF9801 Object &2 in library &3 not found.

CHKOBJ OBJ(LIBNAME/FILENAME) OBJTYPE(*FILE) MBR(*FIRST)

MONMSG     MSGID(CPF9801) EXEC (GOTO CMDLBL(ERROR))

Q: Can we reposition file pointers in CL after reaching EOF? Explain how it works?

Yes, we can reposition the pointer to the file. Upon reaching EOF, or CLOSE command. The CLOSE command closes the file but the file is opened when the next RCVF command is found and the first record from the file is read.