Technical FAQ: Questions about jdbcKona/Sybase
FAQ Index
Problems with jdbcKona/Sybase on UNIX using native threads
I'm using jdbcKona/Sybase on Solaris with native threads, and there
seem to be some problems with using concurrent multiple Statements.
Is there a workaround?
We have determined from customer reports and internal testing that
jdbcKona/Sybase
does not work on native UNIX threads due to underlying problems with
DB-LIB. The general solution is to use jdbcKona/Sybase with green
threads.
On Solaris, however, there is a workaround: native threads will work
if the first database connection is made in the main thread. Then all
other connections will work in other threads.
Character set
incompatibilities when using Solaris Sybase server
We're using jdbcKona/Sybase 3.0.4 with Sybase 11.5 (Adaptive Server
Enterprise). All of our database work is in US English, but we're
getting an error message that says:
Cannot find the requested character set in Syscharsets: name = 'cp850'
Why does WebLogic require the CP850 character set? How can I avoid receiving these error messages?
It's not WebLogic that requires the CP850 character set, it is the
underlying DB-LIB library from Sybase that we use to implement the
driver that is causing the problem. There are slight incompatibilities
between the default character sets installed on the Solaris Sybase
server and those expected by DB-LIB client libraries on other
platforms. This generates a fatal Sybase error upon connecting at the
DB-LIB level. In WebLogic 3.0.4 our driver handles Sybase fatal errors
such as this by throwing a SQLException and returning null as the
Connection. (This default behavior was changed in a later version.)
There are two ways you can avoid these error messages:
- Install the CP850 codeset in your Sybase server.
or
- Upgrade to the WebLogic version 3.1.7 or later. The more recent
version does not throw an exception about the missing CP850 character
set and allows the connection to be made. The error information is
still available by using the java.sql.Connection.getWarnings() method.
Does jdbcKona/Sybase work with Sybase SQL Server 4.9x?
Because Sybase SQL Server 4.9x was developed before the ODBC,
SQL-89, and and SQL-2 standards, it does not support some key features
required under JavaSoft's JDBC
specification. WebLogic does not officially support SQL Server 4.9x,
but some of our customers who are familiar with SQL Server 4.9x report
success in using jdbcKona/Sybase for their SQL Server 4.9x
applications.
WebLogic is aware of the following incompatibilities:
- Methods from the DatabaseMetaData class that return ResultSets
do not work.
- Autocommit cannot be set to false. This is fundamental to the way
that SQL Server 4.9x handles transactions. You must wrap
multistatement transactions in SQL "BEGIN TRANSACTION" and "COMMIT
TRANSACTION".
- Many of the standard SQL keywords are not recognized by 4.9x. For
example, the integer datatype can only be described with the keyword
'int'. You cannot use 'INT', 'integer', or 'INTEGER'.
- The Numeric datatype is not supported.
- Operations on Text/Image data types using SQL queries are more
limited than with newer versions Sybase SQL Server.
Why do I get an Exception when I call getTimestamp()?
I'm using jdbcKona/Sybase and JDK 1.0.2. I am calling a stored
procedure that returns the timestamp as a column in a row result. I
want to pass this timestamp back to a stored proc to use in a database
compare. When I try to use the getTimestamp() method, I get a SQLException. Is there
some way to read and pass back the timestamp without having to use
string conversions?
The problem is that the JDBC
term Timestamp and the SQL Server term Timestamp
have two completely different meanings. In JDBC, Timestamp is a data
type for the storage of absolute or relative time values, analogous to
the Datetime data type in SQL Server. In SQL Server, however,
Timestamp is a binary value that describes when an object (usually a
data page) was last modified.
If you want to select or update a SQL Server Timestamp, treat it as a
Java byte[8] array and use one of the JDBC getBytes() methods to access it.
Note that you also need to upgrade to the latest version of JDK 1.1.
WebLogic is no longer supported under JDK 1.0.2.
Why is the "time" part of the date missing?
I'm returning a date from a database without error, but the "time"
portion of it seems to be missing, for example, I get back "Mon Aug 26
00:00:00 1996". The data in the database has hour, minute, second, and
millisecond information.
If you are using asDate() to
retrieve the date data, this returns a java.sql.Date object, which
doesn't include hh:mm:ss
information. Try using the asTimeStamp() method instead (in the JDBC meaning of Timestamp, not the Sybase
meaning.)
Can I turn off autocommit in my jdbcKona/Sybase application?
I want to turn off autocommit in my jdbcKona/Sybase application to
perform several stored procedure calls within a single transaction.
When I turn off autocommit, however, jdbcKona/Sybase raises an
Exception when I try to get the return values of the individual
stored procs.
Turning off autocommit causes SQL Server to go into "chained" mode,
which may have non-intuitive and sometimes unpredictable results,
especially with stored procedures that were either not designed for
use with chained mode, or were defined when chained mode was not on.
Before you adjust autocommit, you should read the topic "Autocommit"
in the Developers guide for
jdbcKona/Sybase and jdbcKona/MSSQLServer. You should also read the
discussions about chained mode and about transactions in stored
procedures in section 3 of the SQL Server Reference Manual,
"Transactions."
Problems inserting data with jdbcKona/Sybase
I'm using jdbcKona/Sybase to insert some records. I'm getting the
following error when I try to execute the insert statement:
java.sql.SQLException: Length 2107 Exceeds the SQL Server limit of 255
The data you are trying to save is longer than 255 bytes. There are two
SQL Server types (Text and Image) that support data longer than 255
bytes, but there are no methods in the current JDBC
spec that support updates to columns of the corresponding JDBC data
types (Longvarchar and Longvarbinary).
Being able to update Longvarchar and Longvarbinary columns is valuable
enough that we have supplied a public method for it that is not part
of the JDBC API. You can read the details and see a code example in
the jdbcKona/Sybase notes in the Developers guide for
jdbcKona/Sybase and jdbcKona/MSSQLServer.
If this feature is important to your project, please contact jdbc@wombat.eng.sun.com
and ask that it be added to future revisions of the JDBC spec.
How do I get primary key information from a Sybase table?
I'm using Connection.getPrimaryKeys() to retrieve primary key
information from some Sybase tables. I get back a ResultSet, but no
data is in it, that is, the column headings are correct, but there are
no rows in the results.
For Sybase System 10 and 11 and for Microsoft SQL Server, getPrimaryKeys() works if you
created the table with a primary key integrity constraint, for
example:
"create table tprimary (a int, b int, primary key(a,b))"
If you do not create the table this way, there is no way with SQL
Server to determine the primary key.
In addition, getPrimaryKeys() is not implemented for
Sybase 4.9x.
How does jdbcKona/Sybase handle trailing spaces?
I've noticed that jdbcKona/Sybase doesn't handle trailing spaces like
the C language DB-LIB interface I use. DB-LIB trims off trailing
spaces in char fields, but jdbcKona/Sybase does not. Why is the
behavior different?
We call "dbconvert" in DB-LIB with the -2 length flag, which does not
trim any trailing spaces. We considered using the -1 length flag,
which trims all the leading and trailing spaces, but that would
produce a null field if the field was all spaces. We decided that
passing the field exactly as you provide it was a good compromise.
You can trim char fields programmatically if you do not want trailing
spaces.
Using a JIT with HPUX and jdbcKona/Sybase
I am using your Sybase drivers on a HPUX platform and getting
a segfault error. What is going wrong?
There are problems using the jdbcKona/Sybase drivers on the HP
platform with the JavaSoft JIT
(just-in-time compiler). If you invoke Java using
-nojit on the command line you will not have
this problem.
Here is an example for starting a program that has two initial
arguments:
$ java -nojit myProgram myArgument1 myArgument2
Running your program this way will solve the problem.
