Hello,
Some weeks ago I faced difficulties with walk a big number of 
records from a result set.
I was using the function db2_fetch_both in a method of a database adapter
class to retrieve just one record at a time. The total number of records
were: 5647 and when I reach record number 1600 the function crashed
generating the below message in "Actual result" field.
I am copying table's description next:
TMP_TABLE
-----------------------------------------------------------------
| ID        | TYPE        | SIZE        | NULL        |
-----------------------------------------------------------------
| ID        | INTEGER    | 4        | NO        |
| SERVICE    | VARCHAR    | 30        | NO        |
| ID_v        | VARCHAR    | 30        | NO        |
| INFORMATION    | CLOB        | 65536        | YES        |
| EXP_LEVEL    | INTEGER    | 4        | NO        |
| IP4B        | BIGINT    | 8        | NO        |
| MODIFIED    | INTEGER    | 4        | YES        |
| DETAIL    | VARCHAR    | 200        | YES        |
| FALSPOS    | INTEGER    | 4        | YES        |
-----------------------------------------------------------------
When it crashed I received this message from db2_fetch_both
db2_fetch_array() [function.db2-fetch-array]: Fetch Failure
After reported this message to IBM OpenDev I was helped by a OpenDev IBMer who noticed me 
that it wasn't a ibm_db2 module problem, in fact it was a database configuration 
issue. The OpenDev IBMer looked into my DB2 Client CLI TRACE files and found out what was happen.
So I had to modify APP_CTL_HEAP_SZ and everything seems to works fine now.
-- 
Esteban Acosta Villafañe
Area I+D
http://www.openware.biz/opendev
Linkein Profile: http://www.linkedin.com/in/estebanav