Tips Tricks and Little known features in SAP ASE

ISUG-TECH 2014
Conference
Presenter’s Session Title here
Presenter’s name
ISUG-TECH 2015
Conference
Tips, Tricks & Little-Known Features
in SAP ASE
Rob Verschoor
VP, Global DBMS Migration Lead , Platform Solutions Group
(c) 2015 Independent SAP Technical User GroupAnnual Conference, 2015

© 2015 SAP SE. All rights reserved. ISUG-Tech 2015, Atlanta 2
Agenda
 Lots of miscellaneous features!
 Q&A

sp_addtype limit
• Let's say you want to use the same datatype across your stored procedures for variables
and parameters, for example VARCHAR(10000)
• but not necessarily use this in table columns
• Solution: define a user-defined datatype: sp_addtype 'mytype', 'varchar(10000)'
• However:
1> sp_addtype 'varchar_max', 'varchar(10000)' -- on 2KB server
2> go
Msg 17308, Level 16, State 1
Server 'SYB15_2K', Procedure 'sp_addtype', Line 640
Illegal length specified -- must be between 1 and 2048.
1> sp_addtype 'varchar_max', 'varchar(10000)' -- on 8KB server
2> go
Server 'SYB15_8K', Procedure 'sp_addtype', Line 640
Illegal length specified -- must be between 1 and 8192.
• This restriction was meaningless and was removed in 15.7 SP121
• New variable @@maxvarlen contains maximum allowed length of variable

SELECT…WITH RECOMPILE
• Sometimes, you want to force a query plan always to be recompiled.
• Classic solution: sp_recompile for a table referenced in the query
• Downside: affects plans for all other statements referencing this table
• Classic solution: execute or declare the stored proc WITH RECOMPILE
• Downside: affects plans for all statements in the procedure
• Newer solution: EXECUTE('SELECT * FROM …')
• Downside: code becomes more complex; not possible if exec-imm already used
higher up
• Newest solution (15.7 SP130, 16.0 SP01):
SELECT * FROM … WITH RECOMPILE
• Affects only this particular statement

SELECT-INTO inside transaction
• A long-standing restriction:
1> begin tran
2> select * into #t from mytable
3> go
Server 'SYB160', Line 2
SELECT INTO command not allowed within multi-statement
transaction.
• Similar issues:
• SELECT-INTO in a trigger
• CREATE/DROP TABLE in a trigger
• Setting the 'ddl in tran' database option does not affect this!
• Solution in 16.0PL05: new config option 'enable select into in tran' , set to 1
• Also, 'ddl in tran' now allows CREATE/DROP table in a trigger when new config opt = 1

LPAD() & RPAD()
• Padding functions LPAD() and RPAD() added in 15.7 SP130 & 16.0 SP01:
1> select lpad('abc', 6, 'x')
2> go
------
xxxabc
1> select rpad('abc', 4, 'x')
2> go
----
abcx
No longer needed to left-pad a number with zeroes:
select right(replicate('0',8) + convert(varchar,123), 8)
 now use: lpad(123,8,'0')

Nested BIF limit
select isnull(
isnull(sign(
isnull(sign(
isnull(sign(
isnull(sign(
isnull(sign(1),1)),1)),1)),1)),1),1)
Result:
Server 'SYB157', Line 1
Functions may only be nested to level 10.
• This is a hard limit, not configurable
 In 15.7 SP 110, the BIF nesting limit was raised from 10 to 32 (still not configurable)
 In 16.0 SP02, the BIF nesting limit will be raised from 256

Order-By enhancements
• Q: How many 'sort columns' can there be in an order by clause?
select … from mytable
order by col1, col2+100, sqrt(col3), charindex('a', col4),…
• Answer: historically, max. 31
• But as of ASE 15.7 SP50 and SP110: 200
• …. and as of ASE 16.0 : 400
• With compatibility mode enabled, the maximum is still 31

Increased #tables per statement
• Q: How many tables (normal-, work-, proxy-) can there be in a single statement?
• Answer: historically, in 11.9, max. 16; in 12.0, max. 50
• But as of ASE 15.7 SP50 and SP110: 255
• Also: 255 subqueries per statement
• With compatibility mode enabled, the maximum is still 50

Increased #engines in threaded kernel
• The ASE threaded kernel (introduced in 15.7 GA) uses native threads for ASE
server engines
• Allows more threads to be used than heavyweight processes in with the process
kernel
• However, 'max online engines' was still 128 in 15.7...
• The ASE 145.7 documentation said it could be 1024, but that was not correct
• In 16.0 GA, 'max online engines' can be set as high as 1024

PREPARE DATABASE
• Since 12.0: QUIESCE DATABASE … HOLD
• Allows taking consistent copies of DB devices without shutting down ASE
• "storage snapshots", "splitting the mirror", "BCV copy"
• Since 12.5: QUIESCE DATABASE…HOLD…FOR EXTERNAL DUMP
• Allows, for a database initialized with consistent copies of DB devices, loading of log
dumps that were subsequently made in the original server (requires booting the target
ASE server with -q)
• Downside: write actions are frozen during the QUIESCE, affecting applications
• Large customer with >100 EMC Symmetrix devices to split: takes >30 seconds
• New in 15.7 SP130/16.0SP01: PREPARE DATABASE…HOLD
• Same as QUIESCE DATABASE…FOR EXTERNAL DUMP, but does not block any writes
• Requires that the storage layer guarantees that DBMS writes will not be lost an kept in
order, e.g. EMC Symmetrix Enginuity.

Relaxed chained xacts - 16.0
• When ASE runs in chained transaction mode (set chained on), any select statement
(and fetch, insert, update, delete), starts a new transaction.
• In 16.0, no new transaction is started when the SELECT statement:
• References only @variables or @@global variables: select @@error, select @my_var
• References only constants: select 'abc', select 100
• NB: select 'abc' + 'def' still starts a new xact (though select 1+2 does not)
• Calls certain built-in functions:
• get[utc]date()
• current_date()
• current_[big]time()
• current_bigdatetime()
• abs()
• [ase]hostname()
• NB: does not apply to all built-in functions: sign() or rand() still start a new xact!

Pesky 'Transaction count' messages in chained mode
Stored procedures for chained transaction mode:
create proc my_proc as
insert t values (1)
commit
go
sp_procxmode my_proc, 'chained'
go

Stored procedures for chained transaction mode
1> set chained on
2> go
1> select count(*) from t -- start the transaction
2> exec my_proc -- commits the transaction
3> go
-----------
722038
(return status = 0)
Transaction count after EXECUTE indicates that a COMMIT or ROLLBACK TRAN is
missing. Previous count = 1, Current count = 0.
1>
In 15.7 SP110, these messages are suppressed
in chained transaction mode
Pesky 'Transaction count' messages in chained mode
• Update: this message is still printed when the proc is marked with
sp_procxmode… 'anymode' (CR 776856)

CREATE DATABASE…FOR LOAD
• When doing a CREATE DATABASE … FOR LOAD, the idea is that the database will
be overwritten by loading a database dump
• Yet, CREATE DATABASE… FOR LOAD initializes all allocation pages first.
• … and these are overwritten when the dump is loaded
 Conclusion: these writes are pointless
 15.7 SP121: allocation pages no longer initialized  creation is now
instantaneous

KILL
• A long-standing rumour: a stronger version of KILL exists
• E.g. syb_terminate
• Rumour is incorrect! It's a myth…
• See my book "Tips, Tricks & Recipes for Sybase ASE", chapter 3
• Introducing… KILL <spid> WITH FORCE (15.7 SP121)
• Does kill sessions which are unable to check their KILLYOURSELF bit
• Sessions are never killed if they hold a spinlock (could lead to data corruption)
• No downside in using WITH FORCE

PC client downloadable separately
• As of ASE 16.0 GA, the PC client package is not longer bundled with ASE
• Must be downloaded separately; look for "SDK" or "Software Development Kit"

Being creative with permissions (1)
• One of my best tricks: the 'sa_indirect_role' tool
• See www.sypron.nl/grant_sa
• Basically: allow selected non-priviliged users to execute privileged commands
• E.g. running dbcc commands without granting sybase_ts_role
• Uses a combination of ASE features; check the code!
• This is not a security hole, when used responsibly (as with everything)
• Frequently recommended by Sybase TechSupport to customers
• But formally speaking, not supported by Sybase

• New feature in 15.7 ESD#2:
create procedure myproc
with execute as owner
as
…
• This executes the stored procedure with the permissions and roles of the user who
created the procedure
• Default: the user who executes the procedure (execute as caller)
• Create as 'sa', with 'sa_role' etc., execute as a non-priv'd user
• This is a less kludgy, and fully supported, way of achiving much of the same effects
• Yet another supported way to get there: using granular permissions (ASE license
option and configurable feature), also in 15.7 ESD#2

-- allow selected users to shut down the ASE server
create procedure do_shutdown
as begin
-- only allow specific users, see next slide
declare @whoami varchar(30)
select @whoami = suser_name(suid)
from master.dbo.sysprocesses where spid = @@spid
if @whoami in ('jsmith', 'bwhite')
begin
shutdown
end
else
print 'Sorry my friend!'
end
go
grant execute on do_shutdown to public
go
Control access to this procedure
either by explicitly checking the user
or implicitly through grant

• Issue: how to check which user is calling the procedure
• With execute as owner, suser_name() now returns the name of the user who created the
procedure
• Instead, pick up sysprocess.suid
create procedure suser_test
as
begin
select suser_name() 'suser_name',
suser_name(suid) 'suid'
from master.dbo.sysprocesses where spid = @@spid
end
suser_name suid
---------- ---------
sa robv

• Possible applications:
• Reading from MDA tables without granting mon_role
• dbcc commands
• DBA admin commands
• … etc…
• Be aware of permission-related aspects when using execute-immediate in these
stored procedures
• Check out sp_procxmode <procname>, 'dynamic'
• Documentation describes 'Dynamic Ownership Chain' aspects

SAP Exodus DBMS Migration Tool

Supported databases
• Exodus currently supports (v.2.6, Q1 2015):
• Source DBMS:
• Oracle (v.9/10/11/12); >80-90% automatic conversion ratio
• Microsoft SQL Server (v.2000-2012); >90-95% automatic conversion ratio
• IBM DB2 UDB (LUW, v.9.x, most PL/SQL extensions not covered); >70-80% automatic conversion
ratio
• Target DBMS: Sybase ASE, Sybase IQ, or SQL Anywhere
• Exodus is Unicode-enabled for migrated SQL code/schema
• Exodus API is in English only
• Under construction and planned: additional source & target DBMSs

DBMS migration stages
A. Pre-migration complexity/risk assessment  decision to proceed
B. Schema migration
 Performed by Exodus; migrated schema consistent with migrated SQL
C. Data migration (no Exodus support)
• Use SAP/Sybase ECDA/DirectConnect; SAP/Sybase Replication Server; SAP Data Services (etc.)
D. Server-side SQL migration
• Vendor-specific source SQL converted to the target DBMS SQL dialect (SQLScript, T-SQL, Watcom SQL)
• Stored procedure, functions, packages, etc.
• 90%+ of migration effort goes into SQL migration
• Most migration overruns and failures occur here
E. Client-side (application-generated) SQL migration (Exodus support for ad-hoc SQL query conversion)
• Client-side SQL may or may not be hard to capture or locate in app source code
• Fortunately most application-submitted SQL code is usually quite simple
F. Client application (no Exodus support)
 Java/JDBC? Native OCI? Oracle Forms?
G. DBA tools (limited Exodus support)
 Catalog queries not converted
H. Testing (functional, performance) (no Exodus support)




Exodus tool
Exodus run-time components (RTC)
Converted
SQL objects for
target DBMS
(SQL scripts)
Extracted
source DBMS
SQL objects
(SQL scripts)
Converts SQL to native target
DBMS SQL dialect where possible:
-- example: Oracle
SELECT SYSDATE from DUAL;
Converts SQL to run-time components
in target DBMS where needed:
-- example: Oracle
SELECT INITCAP(msg) from MyTable;
-- example: SAP Sybase ASE
SELECT CURRENT_BIGDATETIME()
-- example: SAP Sybase ASE
SELECT
dbo.sp_f_dbmtk_capitalize_word(msg)
from MyTable
Converted to
Converted to

SAP ASE as target DBMS
 SAP ASE does not have a native equivalent of the following PL/SQL features :
 Sequences (*)
 Try-catch exception handling (as in PL/SQL and MSSQL 2005+) (**)
 PL/SQL Packages (and package variables) (**)
 %TYPE declarations (*)
 RECORD and %ROWTYPE datatypes (*)
 Timezone/interval/opaque datatypes (**)
 Buffered PL/SQL output (DBMS_OUTPUT package calls) (*)
 REF Cursors (**)
 Synonyms for tables & views (*)
 Data formatting masks, e.g. with TO_CHAR() (*)
 Nested declarations of SQL functions/procedures (**)
 Parametrized cursor declarations (*)
 Nevertheless, Exodus converts these fully (*) or mostly (**) from Oracle to ASE
 “mostly” means:> 95%.

Exodus Contact Information
Rob Verschoor, D&T Migration Solutions
• Rob.Verschoor@sap.com
or
• ExodusHelp@sap.com
• Also see SCN blogs:
 Google for scn + exodus + verschoor

A Few Audience Quiz Questions….
• What ASE datatype would you use to migrate Oracle's BOOLEAN datatype to ASE?
 TINYINT, not BIT: BOOLEAN can also contain NULL, but BIT can hold only 0 or 1
• How would you migrate a VARCHAR2 parameter in an Oracle stored procedure?
 VARCHAR2 parameters do not have a declared length - so you must pick a length when migrating these
• Can you migrate an Oracle SMALLINT datatype to a SMALLINT in IQ?
 Probably not: Oracle SMALLINT has 38-digit precision, like INT[EGER]. IQ SMALLINT supports the range from -32768 to
32767. So depends on actual values stored.
• What is the difference between Oracle and ASE for the BEGIN TRANSACTION statement ?
 Oracle does not have a BEGIN TRANSACTION statement (it only supports chained xact mode)
• What happens when an unhandled exception reaches a top-level PL/SQL anonymous block?
 An open transaction is rolled back to the implicit savepoint at the start of the anonymous block
• What is the result of this expression: 1/10 ?
 In Oracle: 0.1
 In MSSQL, DB2, ASE, IQ, SQLA: 0
• What is the visible effect of this PL/SQL statement: DBMS_OUTPUT.PUT_LINE(‘Hello!’);
 Nothing, unless set serveroutput on was set, or the generated line is picked up with DBMS_OUTPUT.GET_LINE().

Session-global variables in
ASE

Session-global variables
• Exodus requires session-global variables:
• Scope = session
• Value is retained across client-server trips
• Watcom SQL has CREATE VARIABLE
• ASE has no such feature…
• …or has it?
• Since ASE 12.5:
• set_appcontext()
• get_appcontext()
• rm_appcontext()
• Not designed as session-global variables, but that's what they are
• VARCHAR(255) only
• Uses memory from the procedure cache

Session-global variables
• Exodus run-time components provide an API around these application context
functions, for use by the Exodus generated SQL code
• Handle storage of non-VARCHAR data
• Break up VARCHAR values longer than 255
• Used by Exodus for (among other things)
 Sequences
 Try-catch exception handling (as in PL/SQL and MSSQL 2005+)
 PL/SQL Packages (and package variables)
 Buffered PL/SQL output (DBMS_OUTPUT package calls)
 Migrating the PL/SQL UTL_FILE package

Sequences in ASE (and IQ)
• ANSI 2003 defines the concept of a 'sequence generator'
• DBMS object to generate sequential numbers
• Same basic concept as identity columns, but sequences are stand-alone objects, not part
of a table
• Sequences are supported in various DBMSs: SQL Anywhere, Oracle, MS SQL
• Not available in ASE & IQ
• However: a full sequence implementation can be done using existing ASE features

Sequences in ASE (and IQ)
• Sequence creation (SQL Anywhere syntax):
create sequence MySeq
start at 100
increment by 1
• Basic sequence concepts (SQL Anywhere syntax):
• MySeq.nextval - generates next value for this sequence
• MySeq.currval - contains last value generated for this sequence in the current session
• In SQL terms, these are both functions that can be used as expressions
insert into MyTable (pk, col1)
values (MySeq.nextval, 'Hello World!')

Sequences in ASE
1. Create a table with an identity column (plus other sequence attributes):
create table <name> (
seq bigint identity,
increment_by bigint null,
minvalue bigint null,
maxvalue bigint null,
…
)
2. Insert a row with the attribute values
3. Set the identity counter to the starting value of the sequence
dbcc set_identity_burn_max(…)

Sequences in ASE
4. Create a SQL function to get the next value using reserve_identity()
create function sp_f_nextval (@seqtab varchar(100))
as
begin
set @val = reserve_identity(@seqtab)
return @val
end
• NB: this does not insert a row, but only bumps up the identity counter
• But we need to do one more thing… implement the .currval function
-- keep this value for any subsequent 'currval' calls…
set @dummy = set_appcontext(<name>, @val)

Sequences in ASE
5. Create a SQL function to return the last generated value:
create function sp_f_currval (@seqtab varchar(100))
as
begin
set @val = get_appcontext(<name>, @val)
return @val
end

Sequences in ASE
There's one problem left:
• When a sequence reaches the maximum value, it can cycle back to its starting value
(optionally)
• This can be achieved by running dbcc set_identity_burn_max(…)
However….
• It is not allowed to call DBCC from a SQL Function in ASE
• It is allowed to call DBCC from a stored procedure…
• …but it is not allowed to call a stored procedure from an ASE SQL Function
• How to work around this?

Sequences in ASE
Solution:
• Create a stored proc that pretends to be an extended stored procs
• …since extended stored procs can be called from ASE SQL Functions
• An extended stored proc starts has a name starting with xp_
• They are supposed to map to external DLLs implementing the proc functions
• But they can also be written in SQL!
create proc xp_reset (@seqtab varchar(100))
as
begin
dbcc set_identity_burn_max(...)
end
Call this procedure from the SQL function generating the next sequence value

Sequences in IQ
• Sequences exist in SQL Anywhere 12.x
• However, these cannot be used directly with IQ tables (not clearly documented!)
create sequence MySeq -- really an SA object
go
insert into iq_table (MySeq.nextval, 'Hello!')
go
 Syntax error raised
insert into sa_table (MySeq.nextval, 'Hello!')
go
 OK

Sequences in IQ
• Solution: wrap the sequence call in a SQL Function:
create function sp_f_nextval (@seqtab varchar(100))
as
begin
execute('set @val =' || @seqtab || '.nextval')
return @val
end
insert into iq_table (sp_f_nextval('MySeq'), 'Hello!')
go
 OK

Converting Scalar SQL
Functions to ASE

Converting Scalar SQL Functions to ASE (1)
• ASE’s scalar SQL user-defined functions (UDF) are limited in the features they support
• No DML (INSERT/UPDATE/DELETE)
• No DDL (CREATE TABLE)
• No transaction control (COMMIT/ROLLBACK)
• No non-deterministic BIFs
• No stored proc calls (except xp_ extended stored procedures)
• NB: table-valued SQL UDFs and table variables coming in ASE “Corona” release (2015)
• These limitations can represent a significant migration challenge if many SQL funtions are
used in the source DBMS
• Exodus exploits some boundary areas to convert SQL functions as much as possible anyway
• Main trick: (re)name stored procedures as “xp_” to allow them to be called from a SQL UDF
• Things that still cannot be done:
• SQL Function output parameters  can often be rewritten as a stored procedure, if called only for single
scalar assignment, i.e. not in a SELECT statement (this rewrite is not currently done by Exodus)
• Returning result sets to the client can lead to a TDS machine state error (do NOT try to do this, also not
from a nested procedure called from the UDF)
• Converted PL/SQL exception handling exceptions raised inside a converted SQL function may not be
propagated correctly

• Example: the following SQL UDF would be invalid in ASE
• Contains INSERT statement
• Contains COMMIT statement
CREATE FUNCTION myfunc (@p INT)
RETURNS INT
AS
BEGIN
INSERT INTO MyTab VALUES (@p)
COMMIT
RETURN(@p)
END

• Exodus migrates this function as follows:
CREATE FUNCTION myfunc (@p INT)
RETURNS INT
AS
BEGIN
DECLARE @DBMTK_FUNCTION_RESULT INT
EXECUTE xp_myfunc @DBMTK_FUNCTION_RESULT OUTPUT, @p
RETURN(@DBMTK_FUNCTION_RESULT)
END
CREATE PROCEDURE xp_myfunc (@DBMTK_FUNCTION_RESULT INT OUTPUT, @p INT)
AS
BEGIN
INSERT INTO MyTab VALUES (@p)
COMMIT
SET @DBMTK_FUNCTION_RESULT = @p
RETURN
END
1
2

• Remaining issues:
• There may some spurious warnings returned by ASE, despite the converted
function working correctly
• Currently, any nested stored procedure that is called from a SQL function, must
be named xp_, also on deeper levels
 These issues should be alleviated in SP133, by enabling traceflag 11001
• Do not generate result set output in a stored procedure called from an ASE SQL
function: a TDS state error can occur and abort your session

Converting Try-Catch
Exception Handling to ASE

Converting Try-Catch Exception Handling to ASE (1)
• ASE does not support try-catch exception handling (like Oracle, Watcom, MSSQL, DB2)
BEGIN
…statements…
EXCEPTION
WHEN exception-name THEN ...action...
END
• Yet, Exodus can convert most of Oracle's PL/SQL and MSSQL 2005’s TRY-CATCH exception
handling to an ASE equivalent
• Inserts additional code to detect and propagate exceptions
• The Exodus-generated exception handling code may represent a maintenance challenge
• Exodus user guide provides some guidance
• Very complex exception-handling algorithms may be better migrated manually
• User can always choose not to convert exception handling,
Notes:
• By default, exception handling in ASE SQL functions is not converted
• The body of many SQL functions will be converted to ASE stored procedures anyway, where exception
conversion is enabled by default.

• Automatically converted aspects for Oracle PL/SQL exception handling:
• Oracle exceptions: DUP_VAL_ON_INDEX, NO_DATA_FOUND, TOO_MANY_ROWS,
TIMEOUT_ON_RESOURCE, INVALID_CURSOR, CURSOR_ALREADY_OPEN, ZERO_DIVIDE
• RAISE for user-defined exceptions
• RAISE (without exception name) in an exception handler to re-raise an exception
• RAISE_APPLICATION_ERROR
• Automatic transaction rollback due to unhandled exceptions
• Exception propagation across triggers and nested stored procedure calls
• Not supported for Oracle PL/SQL exception handling:
• Oracle exceptions: ACCESS_INTO_NULL, CASE_NOT_FOUND, COLLECTION_IS_NULL,
INVALID_NUMBER, LOGIN_DENIED, NOT_LOGGED_ON, PROGRAM_ERROR,
ROWTYPE_MISMATCH, SELF_IS_NULL, STORAGE_ERROR, VALUE_ERROR
• Associating of exceptions with an error code (with PRAGMA EXCEPTION_INIT)
• Inside the original exception handling block, RAISE_APPLICATION_ERROR and exceptions occurring
during exception handling, may not be intercepted or propagated
• User-defined exceptions are expected to have unique names across the entire application
• SQLCODE and SQLERRM will often not be exactly identical to Oracle values
:

• Automatically converted aspects for MSSQL 2005+ TRY-CATCH exception handling:
• THROW and RAISERROR in the TRY block
• THROW in the CATCH block to re-raise an exception
• Configurable behavior for BEGIN-END blocks outside TRY-CATCH blocks
• Exception propagation across triggers and nested stored procedure calls
• Not supported for MSSQL 2005+ TRY-CATCH exception handling:
• Exceptions occurring during exception handling in the CATCH block, may not be intercepted or propagated
• Transaction aspects around XACT_STATE() in the catch block; all transactional aspects must be
converted manually
:

Example from PL/SQL application:
CREATE PROCEDURE myproc IS
BEGIN
INSERT INTO Customers VALUES (custID, custName);
[…other statements…]
EXCEPTION
WHEN DUP_VAL_ON_INDEX THEN
DBMS_OUTPUT.PUT_LINE('Error: customer ID already exists!');
ROLLBACK;
END;
Converted to stored procedure
myproc_dbmtk_exception_1234
>>error-checking statements inserted<<

Result in ASE (simplified!)
CREATE PROCEDURE myproc AS
BEGIN
INSERT INTO Customers VALUES (@custID, @custName)
EXEC @rs = myproc_dbmtk_exception_1234 @@ERROR
IF @rs = 1 GOTO end_label
[…other statements…]
end_label:
END
CREATE PROCEDURE myproc_dbmtk_exception_1234 (@err INT) AS
BEGIN
IF (@err = 2601)
BEGIN
PRINT 'Error: customer ID already exists!'
ROLLBACK TRANSACTION
RETURN(1)
END
RETURN(0)
END
1
2
3

• More challenging: nested blocks, with and without exception handlers
• Who handles the exception in a block?
• Where to proceed after an exception was handled or when an unhandled exception remains?
• Exceptions in triggers
BEGIN
BEGIN
…statements…
BEGIN
…statements…
END
…statements…
EXCEPTION
END
EXCEPTION
END

Catching divide-by-zero
• Philosophical debate: should you avoid dividing by zero or catch it when it happens?
• Oracle, MSSQL, DB2 all throw an exception when dividing by zero
• Exodus needs to convert that to a working ASE equivalent
• In ASE, dividing by zero aborts the batch:
1> select 1/0
2> print 'hello'
3> go
Server 'ASE16', Line 1
Divide by zero occurred.
 This means you cannot intercept a div-by-zero in ASE.
 Or can you?

Catching divide-by-zero
• System X comes to the rescue!
• Enable traceflag 3610 : div-by-zero will not abort the batch!
• Starting with ASE 11.0, by default, div-by-zero aborts the batch
1> dbcc traceon(3610)
2> go
1> select 1/0
2> select @@error
3> print 'hello'
4> go
-----------
NULL
Divide by zero occurred.
(1 row affected)
-----------
3607
hello

Tricks are what makes stuff
work!

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