I have just found this advice on the net:
http://www.share.org/proceedings/sh98/data/S1326.PDF
I'm interested mainly in page 19:
Use explicit connection context objects
If connection context object is omitted
a default connection context object is used
default connection context is not thread-safe
can create throughput bottleneck
Example of explicit connection context
// Connection context declaration
#sql context ctx;
...
//get context
myconn=new ctx(Conn1);
...
//use context in SQL
#sql [myconn] {set transaction isolation level read committed};
...
#sql [myconn] cursor001 = {SELECT FKEY,FSMALLINT,FINT
FROM WRKTB01 WHERE FKEY >= :wfkey};
...
//close context but keep database connection
myconn.close(ConnectionContext.KEEP_CONNECTION);
According to the introduction, this advice is just intended for z/OS.
But I thought it may be applicable to DB on Linux or Windows also.
Until now I have written stored procedures like this:
ConnectionContext context = DefaultContext.getDefaultContext();
Connection con = context.getConnection();
#sql{ static sql here};
Looking at the precompiler output, I see that the operations on the
ExecutionContext are in a synchronized codeblock.
If I change my code to use an explicit context, the call to
sqlj.runtime.ref.DefaultContext.getDefaultContext( ); isn't made
anymore, but the rest of the code stays the same (and also the
synchronized codeblock for the ExecutionContext).
So I expect no performance gain because the synchronization overhead
is done anyway (which shouldn't be because I assume I needn't thread
safety for my explicit context object)?
Maybe anyone is able to provide further information on this subject?
Thank you.
