Hi All,

To my understanding, Db2, being a native C++ application (right?), will only use the Java libraries (or the JRE) in such cases as:

-when a Java client requests a remote connection to a Db2 database (via JDBC)

-when external Java stored procedures are being called from within a Db2 database

Have I got this right, or completely at the wrong end of the stick?

Also, does anyone have any ideas how I would check if my Db2 instance/database ever uses any of those Java/JAR files?

What might work here is to set the DIAGLEVEL to 4 (at least temporarily) and then scan the db2diag.log file for any occurrences of the words such as "Java" and "JRE" (and even "JAR"), but not sure how reliable the results would be... any ideas, experiences on this one?

Regards, Damir

------------------------------
Damir Wilder
Senior Consultant
Triton Consulting
London
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Hi All,

To my understanding, Db2, being a native C++ application (right?), will only use the Java libraries (or the JRE) in such cases as:

-when a Java client requests a remote connection to a Db2 database (via JDBC)

-when external Java stored procedures are being called from within a Db2 database

Have I got this right, or completely at the wrong end of the stick?

Also, does anyone have any ideas how I would check if my Db2 instance/database ever uses any of those Java/JAR files?

What might work here is to set the DIAGLEVEL to 4 (at least temporarily) and then scan the db2diag.log file for any occurrences of the words such as "Java" and "JRE" (and even "JAR"), but not sure how reliable the results would be... any ideas, experiences on this one?

Regards, Damir

Hi All,

To my understanding, Db2, being a native C++ application (right?), will only use the Java libraries (or the JRE) in such cases as:

-when a Java client requests a remote connection to a Db2 database (via JDBC)

-when external Java stored procedures are being called from within a Db2 database

Have I got this right, or completely at the wrong end of the stick?

Also, does anyone have any ideas how I would check if my Db2 instance/database ever uses any of those Java/JAR files?

What might work here is to set the DIAGLEVEL to 4 (at least temporarily) and then scan the db2diag.log file for any occurrences of the words such as "Java" and "JRE" (and even "JAR"), but not sure how reliable the results would be... any ideas, experiences on this one?

Regards, Damir

> being a native C++ application (right?),

I was going to confidently(*) say "wrong", but decided to check instead: db2sysc is linked with libC.a (IBM XL C++ Runtime for AIX), so it's either a C++ application, or plays one on TV.

(*) - I mean, it doesn't feel like a C++ application: it doesn't leak memory all over the place, it doesn't eat more memory than necessary, doesn't have a see-saw memory allocation, nor does it choke at the most inconvenient times for a garbage collection. 

Hi All,

To my understanding, Db2, being a native C++ application (right?), will only use the Java libraries (or the JRE) in such cases as:

-when a Java client requests a remote connection to a Db2 database (via JDBC)

-when external Java stored procedures are being called from within a Db2 database

Have I got this right, or completely at the wrong end of the stick?

Also, does anyone have any ideas how I would check if my Db2 instance/database ever uses any of those Java/JAR files?

What might work here is to set the DIAGLEVEL to 4 (at least temporarily) and then scan the db2diag.log file for any occurrences of the words such as "Java" and "JRE" (and even "JAR"), but not sure how reliable the results would be... any ideas, experiences on this one?

Regards, Damir

Fantastic comment, I love it :-)

However, just wondering out loud... weren't Java applications supposed to have a (faulty) garbage collection - and not C++ applications, which should (mis)manage memory on their own?

> being a native C++ application (right?),

I was going to confidently(*) say "wrong", but decided to check instead: db2sysc is linked with libC.a (IBM XL C++ Runtime for AIX), so it's either a C++ application, or plays one on TV.

(*) - I mean, it doesn't feel like a C++ application: it doesn't leak memory all over the place, it doesn't eat more memory than necessary, doesn't have a see-saw memory allocation, nor does it choke at the most inconvenient times for a garbage collection. 

Hi All,

To my understanding, Db2, being a native C++ application (right?), will only use the Java libraries (or the JRE) in such cases as:

-when a Java client requests a remote connection to a Db2 database (via JDBC)

-when external Java stored procedures are being called from within a Db2 database

Have I got this right, or completely at the wrong end of the stick?

Also, does anyone have any ideas how I would check if my Db2 instance/database ever uses any of those Java/JAR files?

What might work here is to set the DIAGLEVEL to 4 (at least temporarily) and then scan the db2diag.log file for any occurrences of the words such as "Java" and "JRE" (and even "JAR"), but not sure how reliable the results would be... any ideas, experiences on this one?

Regards, Damir

Hi All,

To my understanding, Db2, being a native C++ application (right?), will only use the Java libraries (or the JRE) in such cases as:

-when a Java client requests a remote connection to a Db2 database (via JDBC)

-when external Java stored procedures are being called from within a Db2 database

Have I got this right, or completely at the wrong end of the stick?

Also, does anyone have any ideas how I would check if my Db2 instance/database ever uses any of those Java/JAR files?

What might work here is to set the DIAGLEVEL to 4 (at least temporarily) and then scan the db2diag.log file for any occurrences of the words such as "Java" and "JRE" (and even "JAR"), but not sure how reliable the results would be... any ideas, experiences on this one?

Regards, Damir

To answer your questions:
1. When a remote JDBC connection comes to Db2, it is using DRDA protocol so no need for any Java .. it's the driver (db2jcc.jar) which is helping convert client requests and sending using DRDA to the server. 
2.  For Java External routines, Db2 has a process called "db2fmp" which essentially loads up a JVM (which is why no Java external routine can run in unfenced mode) in its own process address space and then creates threads for connections which are calling Java routines/stored procedures.  In the load up phase it does load up the standard libraries included in Java (for I/O, network etc.) from the path  CLASSPATH directory so that it can support the calls made in the Java External SP. In Db2 v11.5 Db2 LUW uses Oracle Java whereas in Db2 v12.1 it's OpenJDK. 

In no case, it needs to load any JAR file for any work .. Db2 just facilitates running of Java routines and just loads them up in the JVM to support the routine calls. For its native work, it's all C libraries (.so or .a). 

Hope this helps.

Rajib

AWS RDS Db2

Hi All,

To my understanding, Db2, being a native C++ application (right?), will only use the Java libraries (or the JRE) in such cases as:

-when a Java client requests a remote connection to a Db2 database (via JDBC)

-when external Java stored procedures are being called from within a Db2 database

Have I got this right, or completely at the wrong end of the stick?

Also, does anyone have any ideas how I would check if my Db2 instance/database ever uses any of those Java/JAR files?

What might work here is to set the DIAGLEVEL to 4 (at least temporarily) and then scan the db2diag.log file for any occurrences of the words such as "Java" and "JRE" (and even "JAR"), but not sure how reliable the results would be... any ideas, experiences on this one?

Regards, Damir

Hi Rajib,

Thanks for your answers, they do make a lot of sense.

And they also confirm what Jan mentioned above (JDBC calls being translated into DRDA protocol).

Regarding the FMPs, we should be able to figure out if they ever (since the last instance restart?) used Java (JVM) by running the command that Mark mentioned (also above):

db2pd -fmpe

Is that right (the command is supposed to give some history on the db2fmp usage, but the documentation is pretty vague on what exactly that is)?

Regards, Damir

To answer your questions:
1. When a remote JDBC connection comes to Db2, it is using DRDA protocol so no need for any Java .. it's the driver (db2jcc.jar) which is helping convert client requests and sending using DRDA to the server. 
2.  For Java External routines, Db2 has a process called "db2fmp" which essentially loads up a JVM (which is why no Java external routine can run in unfenced mode) in its own process address space and then creates threads for connections which are calling Java routines/stored procedures.  In the load up phase it does load up the standard libraries included in Java (for I/O, network etc.) from the path  CLASSPATH directory so that it can support the calls made in the Java External SP. In Db2 v11.5 Db2 LUW uses Oracle Java whereas in Db2 v12.1 it's OpenJDK. 

In no case, it needs to load any JAR file for any work .. Db2 just facilitates running of Java routines and just loads them up in the JVM to support the routine calls. For its native work, it's all C libraries (.so or .a). 

Hope this helps.

Rajib

AWS RDS Db2

Hi All,

To my understanding, Db2, being a native C++ application (right?), will only use the Java libraries (or the JRE) in such cases as:

-when a Java client requests a remote connection to a Db2 database (via JDBC)

-when external Java stored procedures are being called from within a Db2 database

Have I got this right, or completely at the wrong end of the stick?

Also, does anyone have any ideas how I would check if my Db2 instance/database ever uses any of those Java/JAR files?

What might work here is to set the DIAGLEVEL to 4 (at least temporarily) and then scan the db2diag.log file for any occurrences of the words such as "Java" and "JRE" (and even "JAR"), but not sure how reliable the results would be... any ideas, experiences on this one?

Regards, Damir

Hi All,

To my understanding, Db2, being a native C++ application (right?), will only use the Java libraries (or the JRE) in such cases as:

-when a Java client requests a remote connection to a Db2 database (via JDBC)

-when external Java stored procedures are being called from within a Db2 database

Have I got this right, or completely at the wrong end of the stick?

Also, does anyone have any ideas how I would check if my Db2 instance/database ever uses any of those Java/JAR files?

What might work here is to set the DIAGLEVEL to 4 (at least temporarily) and then scan the db2diag.log file for any occurrences of the words such as "Java" and "JRE" (and even "JAR"), but not sure how reliable the results would be... any ideas, experiences on this one?

Regards, Damir