Unit 8. Accessing the DB2 Database Using RPG IV

Copyright IBM Corp. 1996, 2000 8-1

C

op

yrigh

t IBM

Co

rp. 1

99

6, 2

00

08

-2

Unit Objectives - Accessing the DB2 Database

After completing this unit, you should be able to:

• Describe the properties of a physical and logical file

• List and describe the RPG IV operation codes used for file handling

• Code RPG IV programs that read and update database filesOL868000

C

op

yrigh

t IBM

Co

rp. 1

99

6, 2

00

08

-3

OL868105

C

op

yrigh

t IBM

Co

rp. 1

99

6, 2

00

08

-4

OL868110

C

op

yrigh

t IBM

Co

rp. 1

99

6, 2

00

08

-5

DB File Descriptions

• Define record formats for physical and logical files− Single record format for physical files− One or more record formats for logical files

• Coded on DDS at levels below (shown highest to lowest):− Physical file

— File— Record— Field— Key

− Logical file— File— Record— Join— Field— Key— Selection

OL868115

C

op

yrigh

t IBM

Co

rp. 1

99

6, 2

00

08

-6

OL868120

C

op

yrigh

t IBM

Co

rp. 1

99

6, 2

00

08

-7

OL868125

C

op

yrigh

t IBM

Co

rp. 1

99

6, 2

00

08

-8

OL868130

C

op

yrigh

t IBM

Co

rp. 1

99

6, 2

00

08

-9

DDS Field Reference File

�

A*****************************************************************A** Field Reference PF: DICTIONARYA*****************************************************************A R REFFMT TEXT(′ Field Reference File′ ):A** Fields Used in Purchase Order Line Item File, POLINE_PFA POLQTYOO 5 0 TEXT(′ PO Item Quantity On Order′ )A COLHDG(′ Qty′ ′ Ord′ )A POLITMCOST 5 2 TEXT(′ Item Unit Cost′ )A COLHDG(′ Item′ ′ Unit′ ′ Cost′ )A POLDATREC 8 0 TEXT(′ Date Received′ )A COLHDG(′ Date′ ′ Rec′ ′ YYYYMMDD′ )A POLQTYREC 5 0 TEXT(′ Item Quantity Received′ )A COLHDG(′ Qty′ ′ Rec′ )A POLSTATUS 1 TEXT(′ Blank=On Order, C=CompleteA D=Delete I=Incomplete′ )A COLHDG(′ PO′ ′ Ln′ ′ Sts′ )A VALUES(′ ′ ′ C′ ′ D′ ′ I′ )

OL868135

C

op

yrigh

t IBM

Co

rp. 1

99

6, 2

00

08

-10

DDS - PF/LF

�A* PO line item PF: POLINE_PFA REF(DICTIONARY)A UNIQUEA R POLINE_FMT TEXT(′ PO Line Item Record′ )A PONBR RA ITMNBR RA POLQTYOO RA POLITMCOSTRA POLDATREC RA POLQTYREC RA POLSTATUS RA K PONBRA K ITMNBR

�A* PO Open Line Item LF: POOPNLI_LFA R POLINE_FMT TEXT(′ PO Line Item Record′ )A PFILE(POLINE_PF)A K PONBRA K ITMNBRA O POLSTATUS VALUES(′ D′ ′ C′ )

OL868140

C

op

yrigh

t IBM

Co

rp. 1

99

6, 2

00

08

-11

OL868145

C

op

yrigh

t IBM

Co

rp. 1

99

6, 2

00

08

-12

OL868150

C

op

yrigh

t IBM

Co

rp. 1

99

6, 2

00

08

-13

File Operations

• Input Files− Sequential

— READ— SETLL / SETGT— READE / READP / READPE

− Random— CHAIN

• Output Files− EXCEPT− WRITE

• Update Files− All Operations Above− DELETE− UPDATE

• Key Declaration− KLIST / KFLD

OL868205

C

op

yrigh

t IBM

Co

rp. 1

99

6, 2

00

08

-14

File Related BIFs and Extenders

• BIFs

%Found(FileName) Record Found?

%Open(FileName) File open?

%Eof(FileName) EOF (or BOF) Reached?

%Equal(FileName) Key match to search argument?

%Error Previous I/O failed?

• Operation Extenders

�E� Required with %ErrorOL868207

C

op

yrigh

t IBM

Co

rp. 1

99

6, 2

00

08

-15

OL868210

C

op

yrigh

t IBM

Co

rp. 1

99

6, 2

00

08

-16

Explicit Open and Close

�FFileX IF E Disk UsrOpn ** Explicit open of filexC Open (E) FileX **C If not %ErrorC Read FileXC If not %eofC :C :C :C EndIf ** Explicit close of filexC Close (E) FileX **C ElseC Eval Msg = ′ Problem opening FileX - +C Contact Support′C EndIf **C EVAL *inlr = *onC Return

OL868215

C

op

yrigh

t IBM

Co

rp. 1

99

6, 2

00

08

-17

Initial Open at Program Start

�FFileX IF E Disk ** Implicit open of filexC :C : ** Explicit close of filexC Close (E) FileXC If not %errorC :C EndIfC : ** Explicit open of filexC Open (E) FileXC If not %errorC :C EndIf ** Implicit close of filexC Eval *inlr = *onC Return

OL868220

C

op

yrigh

t IBM

Co

rp. 1

99

6, 2

00

08

-18

OL868225

C

op

yrigh

t IBM

Co

rp. 1

99

6, 2

00

08

-19

Data Can Be Accessed

• Externally Described File

− by File Name

− by Record Format Name

• Program Described File

− by File Name onlyOL868230

C

op

yrigh

t IBM

Co

rp. 1

99

6, 2

00

08

-20

OL868235

C

op

yrigh

t IBM

Co

rp. 1

99

6, 2

00

08

-21

Sequential Processing - READ Example

�

FFileX IF E K Disk** ** Read with file nameC Read FileXC If not %EofC :C :C EndIf ** Read with record format nameC Read Format2C If not %EofC :C :C EndIf

OL868240

C

op

yrigh

t IBM

Co

rp. 1

99

6, 2

00

08

-22

Random Processing - Writing Records by Key

�

** Add records to an existing fileFFileX �U�F �A� E K Disk **C Write (E) FileXFmtC If %ErrorC :

�

** ** Output to a new file **FFileY O E DISK **C Write (E) FileYFmtC If %ErrorC :

OL868245

C

op

yrigh

t IBM

Co

rp. 1

99

6, 2

00

08

-23

Random Processing - WRITE by RRN

�

FFileY O E Disk RecNo(Rrn)

DRrn S 2 0 Inz(0)

C :C Eval Rrn = Rrn + 1 <=== Set RRNC Write (E) FileYFmt <=== Write at RRNC If %errorC :

�

FFileY O E Disk

C :C Write (E) FileyFmt <=== Write at EOFC If %errorC :

OL868250

C

op

yrigh

t IBM

Co

rp. 1

99

6, 2

00

08

-24

OL868255

C

op

yrigh

t IBM

Co

rp. 1

99

6, 2

00

08

-25

Positioning File Cursor - SETLL Example

�

FFileX IF E K Disk

C KEY SetLL FileX C If %equal C Read FileX C If not %eof ** Process the recordC EndIfC EndIf ** The LOVAL/HIVAL figurative constants can be used to ** position the file cursor for Keyed accessC *LOVAL SetLL FileXC If %equalC :

OL868260

C

op

yrigh

t IBM

Co

rp. 1

99

6, 2

00

08

-26

OL868265

C

op

yrigh

t IBM

Co

rp. 1

99

6, 2

00

08

-27

Random Processing - CHAIN by Key Example

�

FFileX IF E K Disk ** Chain with file name **C Key Chain FileXC If %Found(FileX)C :

OL868270

Random Processing - Composite Key

� ** PF: FILEXA REF(DICTIONARY)A UNIQUEA R FILEXFMT TEXT(′ FILEX Demo File′ )A FLDA RA FLDB RA DESCRIPT RA ACTIVE RA FLDC RA K FLDAA K FLDBA K FLDC

� ** Search key is composed of (FLDA/FLDB/FLDC)C KeyArg KListC KFld FldXC KFld FldYC KFld FldZC KeyArg SetLL FileXC If %equalC KeyArg Read FileXFmtC If %Found(FileX) ** Process recordC EndIf

C EndIf

OL868275

Copyright IBM Corp. 1996, 2000 8-28

C

op

yrigh

t IBM

Co

rp. 1

99

6, 2

00

08

-29

OL868280

C

op

yrigh

t IBM

Co

rp. 1

99

6, 2

00

08

-30

Random Processing - CHAIN by RRN Example

�

FFileY IF E Disk** ** Chain with file name **C Rrn Chain FileYC If %Found(FileY)C :

OL868285

C

op

yrigh

t IBM

Co

rp. 1

99

6, 2

00

08

-31

OL868290

C

op

yrigh

t IBM

Co

rp. 1

99

6, 2

00

08

-32

OL868295

C

op

yrigh

t IBM

Co

rp. 1

99

6, 2

00

08

-33

Sequential Processing - READE Example

�FFileX IF E K Disk**

C Key Chain Filex C DoW %Found(FileX) C :

C If CustCode = ′ A′C Eval ActCust = ActCust + 1C ElseC Eval InActCust = InActCust + 1C EndIf

C :C Key ReadE FileXC EndDo

OL8682A0

C

op

yrigh

t IBM

Co

rp. 1

99

6, 2

00

08

-34

OL8682A5

C

op

yrigh

t IBM

Co

rp. 1

99

6, 2

00

08

-35

READP / SETGT

�

FFileX IF E K Disk** ** Set greater than pointer with file name **C Key SetGT FileX ** Beginning of File?C DoW not %eofC ReadP FileX ** ** Process the record **C EndDo

OL8682B0

C

op

yrigh

t IBM

Co

rp. 1

99

6, 2

00

08

-36

OL8682B5

SETGT/READPE

�FFileX IF E K DiskD Key S 5AD Msg S 15A**C *Entry PlistC Parm KeyC Key SetGt FileX ** No record key greater than Key argument. Last group encountered?C If not %Found(FileX)C Key Setll FileX **C If %Found(FileX) ** Must be at last group - reposition to end of group againC Key SetGt FilexC Endif **C Endif ** Read records backwards if group existsC If %Found(FileX)C Key ReadPE FileX ** Read group until beginning of group encountered (EOF).C Dow Not %Eof ** Process recordC Eval Msg = Field1 + ′ / ′ + Field2C Msg Dsply ′ *REQUESTER′C Key ReadPE FileXC Enddo **C EndifC Eval *InLR = *ON

OL8682C0

Copyright IBM Corp. 1996, 2000 8-37

C

op

yrigh

t IBM

Co

rp. 1

99

6, 2

00

08

-38

UPDATE

�

FFileX UF E K Disk**DTotalSales S 5 0 INZ(0)****C Key Chain FileXC If %Found(FileX)C Eval TotalSales = TotalSales + SalesC Update Format1C EndIf **

OL8682C5

C

op

yrigh

t IBM

Co

rp. 1

99

6, 2

00

08

-39

DataBase Record Locks

Program can lock only one record per file

Locked:

Read record for update

Released:

Update / write record

Close file

Read another record in same file for updateOL8682D0

C

op

yrigh

t IBM

Co

rp. 1

99

6, 2

00

08

-40

OL8682D5

C

op

yrigh

t IBM

Co

rp. 1

99

6, 2

00

08

-41

OL8682E0

C

op

yrigh

t IBM

Co

rp. 1

99

6, 2

00

08

-42

Read Update File Without Locking Record

�

FVendor_PF UF E K Disk**

C Read (N) Vendor_PF C If Not %Eof

**C ReadE (N) Vendor_PFC If Not %Eof **C ReadP (N) Vendor_PFC If Not %Eof **C ReadPE(N) Vendor_PFC If Not %Eof **C Chain (N) Vendor_PFC If %Found(Vendor_PF)

OL8682E5

C

op

yrigh

t IBM

Co

rp. 1

99

6, 2

00

08

-43

Releasing a Locked Record

�

FVendor_PF UF E K Disk**

C KEY Chain Vendor_PF**

C If %Found(Vendor_PF) C : C Unlock Vendor_PF

** C EndIF

OL8682F0

C

op

yrigh

t IBM

Co

rp. 1

99

6, 2

00

08

-44

Considerations When Releasing Locked Record

• has record changed since read?

• if so, how to detect record change?

• use timestamps, flags, record image comparison?OL8682F5

C

op

yrigh

t IBM

Co

rp. 1

99

6, 2

00

08

-45

DELETE

�

FFileX UF E K Disk**DTotalSales S 5 0**** ** Delete current record based on CHAINC Key Chain FileX **C If %Found(FileX)C Delete FileXC EndIF

** Delete record using file keyC Key Delete FileXC If Not %Found(FileX)

OL8682G0

C

op

yrigh

t IBM

Co

rp. 1

99

6, 2

00

08

-46

OL8682G5

C

op

yrigh

t IBM

Co

rp. 1

99

6, 2

00

08

-47

OL8682H5

C

op

yrigh

t IBM

Co

rp. 1

99

6, 2

00

08

-48

CRTPF/CHGPF Parameters

�

DLTPCT (*NONE) ALWDLT* (*YES)(deleted-records-threshold-%) (*NO )

REUSEDLT (*NO) SIZE (#recs incr. #incr)(*YES)

WAITFILE (*IMMED)LVLCHK (*YES) (*CLS)

(*NO) (number-of-seconds)

EXPDATE* (*NONE) WAITRCD (*IMMED)(expiration-date) (*NOMAX)

(number-of-seconds)ALWUPD* (*YES)

(*NO ) SHARE (*YES)(*NO )

�* CRTPF only�

OL868305

C

op

yrigh

t IBM

Co

rp. 1

99

6, 2

00

08

-49

OL86810L

C

op

yrigh

t IBM

Co

rp. 1

99

6, 2

00

08

-50

Unit Summary

Having completed this unit, you should be able to:

• Describe the properties of a physical and logical file

• List and describe the RPG IV operation codes used for file handling

• Code RPG IV programs that read and update database filesOL863ZZZ