Skip to main content

Ingres resource limiting : Part2 (Ingres resource limiter 'maxio')

There was a suggestion to use the resource limiter (set maxio) as to capture and handle the exception thrown when the threshold is reached.

That was a great suggestion but soon discovered several limitations as far as ABF-4GL goes (reports cannot use it) :
In my topframe I am setting the maxio to a threshold value by using the 'set maxio' directive and I programm my errorhandler using iiseterr() to trap the error issued when that threshold is reached.

But,as the manual states, 'Your error-handling routine must not issue any database statements in the same session in which the error occurred. If it is necessary to issue database statements in an error handler, open or switch to another session' OR 'Do not issue any
query statements from inside your error handler routine because the application occasionally "hangs" or returns runtime errors.' OR 'User code in the handler cannot issue database statements for the session from which
the handler was called.'

So in essence if the maxio limit is reached but the user wishes to continue despite the warning there is now way to reset to 'set nomaxio' from within my ESQL programm.
Nor,can I fire a database event,log the error in a table etc

Let's move to "If it is necessary to issue database statements in an error handler, open or switch to another session" part. I connect to a new session where I can issue database statements,do some clean up work,disconnect successfully.
I set the current session as active using
exec sql SET_SQL ( session = :session_id)
before my handler returns and I get a
'Attempt to switch to a non- existent session. (E_LQ00BE) ' error.

The session_id was retrieved by inquire_sql and contains the value '-1' which is the value set by ABF.I must agree that it "does not conform to the rules for session numbers that are stated in the SQL Reference Manual" (quoting a post in comp.database.ingres)

So I thought that because -1 is not the real session id I should retrieve the real session number.
I issued a select dbmsinfo('session_id') inside my topframe and put the return value inside a global variable which is then communicated to my 3GL programm by using 'exec 4gl get global variable'.
However the session id returned by dbmsinfo is a string representation of a hex number ie '0A089EA0' so I had to converted it to an integer inside my Esql/C procedure hence getting the real session id, confirmed by checking the active sessions of the iimonitor's output.

Tried 'exec sql SET_SQL ( session = :session_id)' again with the correct id,but the
'Attempt to switch to a non-existent session. (E_LQ00BE) ' error persisted.

Tried to connect to that session :
'exec sql connect psnodb session :session_id'
and the error message now is 'Attempt to connect to existing database session 168337056. (E_LQ00BA)'.

It seems like I've run into a dead end because from within the ESQL error handler one cannot use database statements for the current session, nor switch to another session and reconnect back to the old one .


Popular posts from this blog

Serverless JavaScript

We recently joined in an interesting two-hour long conversation about Serverless JavaScript led by Steve Faulkner of Bustle who answered questions on Bustle, the Shep framework, the mindset behind the AWS Lambda infrastructure, and related topics.

The discussion took place on the Sideway conversation-sharing platform on January 6th. Here we present the best takeaways from the session which really should be taken notice of by anyone working on AWS.

Steve Faulkner:
At Bustle we serve over 50 million unique readers per month through a "serverless" architecture based on AWS Lambda and Node.js.  Of course there are still servers but we don't manage them. This shift has allowed us to develop products faster and decreased the cost of our infrastructure. I'll answer any questions about how we made this transition and how it has worked out. I'll also discuss some of the tools and best practises including our open source framework shep

Eran Hammer:
When would you…

Export your Wunderlist tasks with XPath

As brought up in this ProductHunt thread, the news is that Wunderlist is going to be deprecated in favor of the new Microsoft To-Do note taking platform.

This is what Wunderlist support had to say in response to my inquiry on Wunderlist's future:

"Now that the next evolution of Wunderlist is here, in the form of Microsoft To-Do Preview (, Wunderlist will no longer receive any updates or bug fixes and will eventually be retired. It won’t happen in the next few months and we’ll be sure to give our users plenty of notice beforehand. In the meantime, you can continue to use Wunderlist normally. Of course, we’d also love for you to try To-Do and let us know how you like it – and how we can improve it. While Wunderlist will continue to exist alongside To-Do for the time being, support for Wunderlist will eventually be removed. Not to worry, though! We will inform all Wunderlist users prior to shutting down service. You'll have ample opport…

Google's Cloud Spanner To Settle the Relational vs NoSQL Debate?

Cloud Spanner is a new proposition for database as a service that emphatically offers "Relational with NoSQL scaling". Will Google come to dominate yet another market?

Once upon a time there was only one kind of database management system, the RDBMS, "R" for relational. Despite its resilience and trustworthiness, it had its shortcomings; it did not scale well, and the relational model it served proved inadequate in the dawn of the Big Data era for handling massive amounts of schema-less, unstructured data.
For this and a few other reasons, a new breed of DBMS's emerged, one that could handle the avalanche of big data, based on the notion of the key-value pair, and doing so by scaling horizontally. But, in order to become versatile, this new breed of management systems had to forgo the safety of the ACID and the cosiness of SQL, both long term partners of the relational model. full article on i-programmer