DB2 UDB for z/OS Version 8 Performance Topics - IBM Redbooks

7.4.4 ODBC support for 2 MB SQL
7.4.5 SQLcancel
Currently, the maximum size in bytes of an SQL statement string (including white spaces)
allowed on the SQLPrepare, SQLExecDirect and SQLNativeSql APIs is 32765. DB2 V8
running in NFM supports a maximum statement size of 2MB (2097152). DB2 V8 ODBC will
now support SQL statements up to 2 MB in size when connected to DB2 V8 servers running
in NFM.
This enhancement requires APAR PQ88582/PTF UQ91257.
The SQL cancel() statement allows an ODBC/CLI or JDBC application to cancel an SQL
request long running on a DB2 server. Note that SQL cancel() is at a more granular level than
the DB2 -CANCEL THREAD command. SQLcancel() only rolls back the currently executing
SQL statement, not the entire unit of work. In addition, the thread is not destroyed in the
process, but is allowed to continue processing.
If the database server is not in an interruptible state, the request completed before DB2 can
interrupt, or the request is not interruptible, then DB2 returns a DRDA reply message back to
the client confirming the attempt. A new SQLCODE -952 is returned if the SQL statement was
interrupted (rollback worked). If the SQL statement just reads data (not write), then we issue
-952 even if rollback did not work.
Currently only dynamic SQL statements are interruptible. Stored procedures cannot be
interrupted. Transaction level SQL statements like CONNECT, COMMIT and ROLLBACK
cannot be interrupted. Even BIND PACKAGE cannot be interrupted.
7.5 XML support in DB2 for z/OS V8
7.5.1 XML extender
For the past few years, XML has increasingly become the de facto data format on the internet,
on corporate intranets, and for data exchange.
Up to DB2 V7, you could use LOB or CLOB columns to store XML documents in relational
tables. It was recommended that character objects be used to enable use of SQL character
functions, such as concatenate, on the XML CLOBs.
If you needed XML data from traditional relational databases, you had to create an application
to convert the DB2 data to the XML format or use the XML extender.
DB2 V8 provides SQL/XML publishing functions to help with XML document composition
directly from DB2 data.
Up to DB2 V7, you could use the XML extender feature for manipulating XML data into and
out of DB2.
Description
The XML extender is a set of external programs which are defined to execute as stored
procedures and user-defined functions, invoked using SQL statements. The functionality
provided by the XML extender is very rich, including intact storage, shredding to relational
tables, indexing and searching. However, this function is still seen as an “add on” and the
external routines do not perform as well as code inside the database engine.
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