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APM v8 Installer overwriting size of bufferpool TBSMCFG16KBP

Technical Blog Post


Abstract

APM v8 Installer overwriting size of bufferpool TBSMCFG16KBP

Body

When installing APM v8.x, if you decide to use an existing DB2 installed on a remote system, you must follow the steps in the APM Manual,

chapter called "Connecting to a remote DB2 server".

https://www.ibm.com/support/knowledgecenter/SSHLNR_8.1.4/com.ibm.pm.doc/install/install_server_mydb2.htm#install_server_mydb2

 

One of the steps you are requested to perform before installing APM, is about changing the bufferpool size for database SCR32, using value 10000.

 

db2 alter bufferpool TBSMCFG16KBP IMMEDIATE size 10000

 

Actually, this value should depend on the environment size.

There is a table in the 8.1.4 on-premise online documentation that shows the DB2 bufferpool sizes chosen by the server_size.sh script:

https://www.ibm.com/support/knowledgecenter/SSHLNR_8.1.4/com.ibm.pm.doc/install/admin_jvmheapsize_apmadmin.htm#scmai_adminpassword

 

For the bufferpool TBSMCFG16KBP, it sets 1000 pages for small, 5000 for medium, and 10000 for large environments.

 

In any case, let's suppose we used the value 10000 as suggested in the manual.
When we perform APM installation on the target host, at the end of the installation we will see that the bufferpool size for TBSMCFG16KBP may be not the same

we previously manually set.

You can check the bufferpool size using command:

 

SELECT * FROM SYSCAT.BUFFERPOOLS

 

after connecting the target database (in this case SCR32).

Why does it occur ?

It occurs because install.sh is calling setup-dbconfig-linux_64.bin even through the database is remote.


Setup-dbconfig will try to create all of the different pieces of the SCR database but since all of the tables, indexes, views,
etc are already created, these steps fail, with the exception of the following statements:

ALTER BUFFERPOOL IBMDEFAULTBP IMMEDIATE size 5000;
ALTER BUFFERPOOL TBSMCFG16KBP IMMEDIATE size 1000;
ALTER BUFFERPOOL TBSM4KBP IMMEDIATE size 1000;
ALTER BUFFERPOOL TBSM32KBP IMMEDIATE size 1000;
ALTER BUFFERPOOL TBSMSCR16KBP IMMEDIATE size 30000;

So they are actually executed and the bufferpool size for TBSMCFG16KBP is set to 1000.
There is no way to avoid it at the moment.

Post install you should go back to your remote DB2 and run the following commands to restore the wanted values.

db2 connect to SCR32
db2 UPDATE DATABASE CONFIGURATION FOR SCR32 USING LOGSECOND 25
db2 alter bufferpool TBSMCFG16KBP IMMEDIATE size 10000
db2 alter bufferpool TBSMSCR16KBP IMMEDIATE size SCR32_PAGE_COUNT
db2 disconnect SCR32

SCR32_PAGE_COUNT:
The buffer pool page count (16 K page sizes): 15000 for small, 30000 for medium, and 30000 for large.

The product manual is going to be changed to include above steps.

Hope it helps.

 

 

 

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