DB2 Temporary tablespace

We encountered this issue:
[DB2]A temporary table space with sufficient page size does not exist.

By default, we create a temporary tablespace defines as User temporary tablespace. We were able to fix this by adding a System temporary tablespace using WEBMBUFF.

Questions:

What is the differnce between SYSTEM and USER temporary tablespaces?
Why would creating a System versus User temporary tablespace fix this?
CREATE 
PROCEDURE XYZ_TABLESPACES_TMP() 
    BEGIN    
      DECLARE V_COUNT INT DEFAULT 0;
      DECLARE STATEMENT VARCHAR(1000);
      SELECT COUNT(*)  INTO V_COUNT  FROM SYSIBM.SYSTABLESPACES
      WHERE TBSPACE = 'XYZTEMP';
      IF (V_COUNT = 0) THEN
        SET statement =  'CREATE USER TEMPORARY TABLESPACE XYZTEMP PAGESIZE 32K MANAGED BY SYSTEM USING (''XYZTEMP'') BUFFERPOOL  XYZBUFF';
       EXECUTE IMMEDIATE statement; 
    END IF;             
   END
/
 
as
 
CREATE 
PROCEDURE XYZ_TABLESPACES_TMP() 
    BEGIN    
      DECLARE V_COUNT INT DEFAULT 0;
      DECLARE STATEMENT VARCHAR(1000);
      SELECT COUNT(*)  INTO V_COUNT  FROM SYSIBM.SYSTABLESPACES
      WHERE TBSPACE = 'XYZTEMP';
      IF (V_COUNT = 0) THEN
        SET statement =  'CREATE SYSTEM TEMPORARY TABLESPACE XYZTEMP PAGESIZE 32K MANAGED BY SYSTEM USING (''XYZTEMP'') BUFFERPOOL  XYZBUFF';
       EXECUTE IMMEDIATE statement; 
    END IF;             
   END
/

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mbevilacquaAsked:
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Kent OlsenConnect With a Mentor Data Warehouse Architect / DBACommented:
Hi mbevilacqua,

The System and User temporary space areas are used for completely different things.  Though the lines can get a little blurry as to which type of space is requred for a particular operation.

As a query is executed, most operations are done in user temp space.  When a table (or subtable) is sorted, the results are written back to the user temp.  (Note that the table may be sorted even if the SQL didn't include a SORT clause.)  The sort operation itself may use space in the system temp area.  If the entire sort doesn't fit into memory, then the system temp is used as a sort of "paging" area for the sort process.

Without seeing your SQL it's impossible to know why it required SYSTEM temp space, but there are perfectly legitimate reasons.


Good Luck,
Kent


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mbevilacquaAuthor Commented:
So our applicaiton needs to use 32k pagesizes. Does this mean we need to create a USER 32k temp and a SYSTEM 32k temp?

SQL: select xyzcolumn from tablexyz where xyzcolumn=1 order by xyzcolumn
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momi_sabagCommented:
the best way to find out would to just try it with only the system temp tablespace
if it would work - you don't need the user tablespace
if it won't work, you do need it
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mbevilacquaAuthor Commented:
Easier said then done. We produce software and ship it to hundreds of customers. We need to know at ship time is it is required. I guess we can do a complete regresion test and see if converting the create from USER to SYSTEM causes any problems, but that is a big task.

The odd thing is that we have only used USER temp space for years. This is the first time we have seen this issue and the requirement for a System temp space.
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Kent OlsenData Warehouse Architect / DBACommented:
Hi mbevilacqua,

There's always SYSTEM temp space.  It's just that the default amount is just fine for most installations.

Creating a user temporary table in the SYSTEM temporary space is a bad idea, particularly when you're distributing "shrink wrapped" software and have little control over the user environments.  Better plans are to create another tablespace specifically for the temporary tables or just allow DB2 to manage the space.


Kent
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mbevilacquaAuthor Commented:
We use regular table spaces with page size 32K to keep our data. So would we need to create system temporary table space with same page size or Is it enough IBM default table space 'TEMPSAPCE1' which is system temporary with page size 4k?
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Kent OlsenData Warehouse Architect / DBACommented:
The system temp space should be fine with 4K pages.  It doesn't typically hold user (row) data.


Kent
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