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Redundant data in all application servers

Former Member
0 Kudos

Hello,

for tables, I can choose buffering or not and the buffering type as well.

An example: In a system with two ore more application servers, a buffered table is read for the first time and thus loaded to one application server. Thus the table (or individual tuples)is buffered in this application server. Although the table was not requested by clients logged on other application servers, do all other application servers load this table from the database as well?

What happens if a buffered table is only hold on one application server and changend. This change is written into the DDLOG file. Other application servers read this. Althoug they have not buffered that table yet, do they now load it into their buffer...

This would make no sense, but I did not find the clear message anywhere that application servers only load the tables that are requested from it...

Thanks,

holger

1 ACCEPTED SOLUTION

christian_wohlfahrt
Active Contributor
0 Kudos

Hi Holger!

Do all other application servers load this table from the database as well?

No.

Do they now load it into their buffer?

No.

Buffer is only filled, if an (read?) access is done. Then only smallest amount of data according to buffer settings is read (single / generic / full).

So it can happen, that 'simple' select single triggers reading a whole DB table.

DDLOG synchronization: here is the question, if it is a push or pull logic. Does DB server distribute DDLOG to all application servers for all buffered tables, or do application server ask DDLOG status for currently buffered tables in memory.

I don't know, but my guess is second approach (because it's less work).

Regards,

Christian

1 REPLY 1

christian_wohlfahrt
Active Contributor
0 Kudos

Hi Holger!

Do all other application servers load this table from the database as well?

No.

Do they now load it into their buffer?

No.

Buffer is only filled, if an (read?) access is done. Then only smallest amount of data according to buffer settings is read (single / generic / full).

So it can happen, that 'simple' select single triggers reading a whole DB table.

DDLOG synchronization: here is the question, if it is a push or pull logic. Does DB server distribute DDLOG to all application servers for all buffered tables, or do application server ask DDLOG status for currently buffered tables in memory.

I don't know, but my guess is second approach (because it's less work).

Regards,

Christian