Error Management Features

8/12/2019 Error Management Features

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Copyright 2000-2006 Steven Feuerstein - Page 1

OPP 2007February 28 March 1, 2007

San Mateo Marriott

San Mateo, California

An ODTUG SP* Oracle PL/SQL

Programming Conference

*SP Seriously PracticalConference

For more information isit !!!"o#tu$"com or call %10&'(2&7'''

O)+ -alei#osco.e/une 18 21, 2007

Pre&conference an#s&on rainin$ & /une 1 17

ilton )aytona each Oceanfront 3esort)aytona, Flori#a

WOW-Wide Open World, Wide Open Web


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Ma4in$ the Most of

Oracle P56S5

rror Mana$ement Features

Steven FeuersteinPL/SQL EvangelistQuest Software

[email protected]


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Ten Years Writing Ten Bookson the Oracle PL/SQL Language


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How to benefit most from this class

Watch, listen, ask questions.

Download the training materials and supporting scripts:

http://oracleplsqlprogramming.com/resources.html

"Demo zip": all the scripts I run in my classavailable athttp://oracleplsqlprogramming.com/downloads/demo.zip

Use these materials as an accelerator as you venture intonew territory and need to apply new techniques.

Play games! Keep your brain resh and active by miing

filename9from9#emo9:i."s;l


5/34Copyright 2000-2006 Steven Feuerstein - Page 5

Manage errors effectiel! an" consistentl!

# signiicant challenge in any programmingenvironment.

Ideally# errors are raised# handled#logged and communicated in aconsistent# robust manner

$ome special issues or P%&$'% developers

$he %&'%($I)* datatype

+ow to ,ind the line on which theerror is raised-

'ommunication with non(/S0 hostenvironments



#chieing i"eal error management

Deine your requirements clearly Understand P%&$'% error management

eatures and ma"e ull use o what P%&$'%

has to oer #pply best practices.

'ompensate ,or (/S0 wea1nesses

Single point o, de,inition: usereusable components to ensureconsistent# robust error management



$efine !our re%uirements clearl!

When will errors be raised, when handled( Do you let errors go unhandled to the

host# trap locally# or trap at the topmost level-

)ow should errors be raised and handled(

2ill users do whatever they want or willthere be standard approaches that

everyone will ,ollow- Useul to conceptuali*e errors into three

categories:


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$ifferent t!&es of e'ce&tions

Deliberate

$he code architecture itsel, deliberatelyrelies on an e3ception. %3ample:4$5FI%.6%$5I*%

Unortunate It is an error# but one that is to be

e3pected and may not even indicate aproblem. %3ample: S%%'$ I*$) 7

*)5D8$85F)4*D Unepected

8 "hard" error that indicates a problem

e


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PL/SQL error management features

Deining eceptions

+aising eceptions

)anding eceptions ceptions and D-%


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Qui() Test !our e'ce&tion han"ling know*how

DECLARE

aname VARCHAR2(5);

BEGIN

BEGIN

aname := 'Justice';

DB!"#$%&$%&$%"LINE (aname); ECE&%I#N

HEN VAL$E"ERR#R

%HEN

DB!"#$%&$%&$%"LINE ('Inne* +,-c.');

END;

DB!"#$%&$%&$%"LINE ('/at e**-*0');

ECE&%I#N HEN VAL$E"ERR#R

%HEN

DB!"#$%&$%&$%"LINE ('#ute* +,-c.');

END;

e


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$efining +'ce&tions

he /0P123 is a limited type o data. +as ;ust two attributes: code and

message.

9ou can 8IS% and handle ane3ception# but it cannot be passed asan argument in a program.

4ive names to error numbers with the

/0P1235131 P+#4-#.

CREA%E #R RE&LACE &R#CED$RE u1"3-*"e1t (

e1t"in IN em1,-4eee1a*tment"i%6&E

7 ne8sa,"in IN em1,-4eesa,a*4%6&E

)

I!

+u,."e**-*s ECE&%I#N;

&RAGA ECE&%I#N"INI% (+u,."e**-*s7 92


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,aising +'ce&tions

+#1$ raises the speciied eception byname.

8IS%< reraises current e3ception.'allable only within the e3ception

section.

+#1$5#PP%10#1235++2+

'ommunicates an application speci,ic

error bac1 to a non(/S0 hostenvironment.

%rror numbers restricted to the=>#??? =>#>>> range.


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-sing ,#.S+#PPL.0#T.O1+,,O,

I> :NE+i*t/ate ? ADD"#N%H! (!6!DA%E7 9 @ < @ 2)

%HEN

RAI!E"A&&LICA%I#N"ERR#R

(927 Em1,-4ee must +e ;

0ommunicate an error number and message to a

non6P%&$'% host environment.

$he ,ollowing code ,rom a databasetriggers shows a typical !and problematicusage o, 8IS%58((I'8$I)*5%):

RAI!E"A&&LICA%I#N"ERR#R (num +ina*4"intee*7 ms Fa*c/a*27

.ee1e**-*stac. +--,ean e3au,t >AL!E);


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Qui(2 #n +'ce&tional Package

$o 1 create the valerr pac"age and then eecute theollowing command. What is displayed on the screen(

&ACAGE Fa,e**

I!

>$NC%I#N

et RE%$RN VARCHAR2;

END Fa,e**;

!L? EEC$%E 1, (Fa,e**et);

&ACAGE B#D6 Fa,e**

I! F VARCHAR2() := a+c;

>$NC%I#N et RE%$RN VARCHAR2 I!

BEGIN

RE%$RN F;

END;

BEGIN

1, ('Be3-*e I s/-8 4-u F');ECE&%I#N

HEN #%HER! %HEN

1, (%*a11e t/e e**-*);

END Fa,e**;

alerr".4$

alerr2".4$


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Han"ling +'ce&tions

he /0P123 section consolidates all errorhandling logic in a bloc". @ut only traps errors raised in the e3ecutable

section o, the bloc1.

$everal useul unctions usually come into play: S0')D% and S0% D@S54$II$9.F)8$5%)5S$8'A

D@S54$II$9.F)8$5%)5@8'A$8'%

he D7-$5++%24 pac"age 0uic1 and easy logging o, D errors

he #8+ $+9+++2+ trigger Instancewide error handling


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$BMS-T.L.TY error functions

4et the ull error message withD7-$5U1%1.82+-#5++2+5$#0K

S0% might truncate the message.

4se S0% went you want to obtain the

message associated with an error number. 8ind line number on which error was raised with

D7-$5U1%1.82+-#5++2+57#0K+#0

Introduced in )racleB>g elease =# this

,unction returns the ,ull stac1 o, errors withline number in,ormation.

Formerly# this stac1 was available only i, youlet the error go unhandled.

bac4trace"s;l


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$BMS+,,LO3 4Oracle56g,78

#llows D-% statements to eecute againstall rows, even i an error occurs. $he )6 %)S clause speci,ies how

logging should occur.

4se the D@S5%)6 pac1age toassociate a log table with Doperations on a base table.

-uch aster than trapping errors, logging,

and then continuing&recovering. 3ote: 82+#%% with $#9 /0P123$

oers similar capabilities.#bms9errlo$"*


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+'ce&tions an" $ML

D-% statements generally are notrolled bac" when aneception is raised. $his gives you more control over your

transaction.

+ollbac"s occur with...

4nhandled e3ception ,rom the outermost(/S0 bloc1#$ND

%HEN

e**1.*ec-*"an"c-ntinue(

!LC#DE7

' N- c-m1an4 3-* i ' %#"CHAR (F"i));

HEN #%HER!

%HEN

e**1.*ec-*"an"st-1;

END;

he #eelo.er sim.ly

de!cribe!

the #esire# action"

S if i th


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S&ecif!ing the error

)ow should 1 speciy the application6speciic error 1 need to raise(

; >>> all the time(; Pic" one o those ?>>> numbers rom

6=>@@@ to 6=>>>>(; Use any positive error number

besides ? and ?>>(; Use error namesinstead o numbers(

# i" h " "i f 76 111 +


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#oi" har"*co"ing of *76


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, i /h "l b b >


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,aise/han"le errors b! number===or name>

he above trigger ragment illustrates a common

problem: )ard6coding o error numbers andmessages.

0ertainly, it is better to use named constants, as in:

BEGIN

I> em1,-4ee"*1is"t-"4-un (:ne8/i*e"ate)%HEN

RAI!E"A&&LICA%I#N"ERR#R (

9257'6-u must +e at ,east < 4ea*s -,');

END I>;

BEGIN

I> em1,-4ee"*1is"t-"4-un (:ne8/i*e"ate)

%HEN RAI!E"A&&LICA%I#N"ERR#R (

em1,-4ee"*1en"t--"4-un

7 em1,-4ee"*1em"t--"4-un);

END I>;

ut no! !e hae acentrali:e#

#e.en#ency"

, i i b


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,aising errors b! name

Use an error name Bliteral valueC. $he code compiles now.

ater# I de,ine that error in the

repository. *o central point o, ,ailure.

Downsides: ris" o typos, runtimenotiication o undeined error.

BEGIN

I> em1,-4ee"*1is"t-"4-un (:ne8/i*e"ate)%HEN

M"*untime*aise"e**-* (

'E&L#6EE9%##96#$NG'

7 name"in =?'LA!%"NAE'

7 Fa,ue"in =?:ne8,ast"name);

END I>;

n


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Summar!2 an +'ce&tion Han"ling #rchitecture

-a"e sure you understand how it all wor"s

%3ception handling is tric1y stu,,

$et standards beore you start coding Its not the 1ind o, thing you can easily add in

later

Use standard inrastructure components %veryone and all programs need to handle

errors the same way

a"e ull advantage o error management eatures.

S8H% %&'%($I)*S# D@S5%)6#D@S54$II$9.F)8$5%)5@8'A$8'%...

DonAt accept the limitations o 2racleAs currentimplementation.

More PL/SQL Please)


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More PL/SQL< Please)

7ryn %lewellyn, P%&$'% Product -anager,will hold orth at the Database 4uru %ounge

at ?=:E> P- today.

Located in the Database Demorounds area which is in the !est"all at the rear# dead center andunder the area D sign


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OPP 2007February 28 March 1, 2007San Mateo Marriott

San Mateo, California

An ODTUG SP* Oracle PL/SQL

Programming Conference

*SP Seriously PracticalConference

For more information isit !!!"o#tu$"com or call %10&'(2&7'''

O)+ -alei#osco.e/une 18 21, 2007

Pre&conference an#s&on rainin$ & /une 1 17

ilton )aytona each Oceanfront 3esort

)aytona, Flori#a

WOW-Wide Open World, Wide Open Web

Documents

Error Management Features