You can use the ASYNCJ parameter to control the usage of the temporary
result writer.
The ASYNCJ parameter has the following options:
- *ANY—allows the temporary result writer jobs to be used for database queries
involving distributed files.
- *DIST—allows the temporary result writer jobs to be used for database
queries involving distributed files.
- *LOCAL—allows the temporary result writer jobs to be used for queries
of local files only. Although this option is allowed, currently there is no
system support for using temporary result writers for local query processing.
*LOCAL was added to disable the temporary result writer for distributed queries,
yet still allow communications to be performed asynchronously.
- *NONE—never use the temporary result writer. In addition, when distributed
processing is performed, communications are performed synchronously. This
can be very useful when analyzing queries, because it allows query debug messages
from remote systems to be returned to the local system.
The following example shows you how to disable asynchronous job usage
for distributed file processing:
CHGQRYA ASYNCJ(*LOCAL)
This
command prevents asynchronous jobs from being used for queries involving distributed
files.
The following example shows you how to completely disable asynchronous
job usage:
CHGQRYA ASYNCJ(*NONE)
This
command prevents asynchronous jobs from being used for any queries. In addition,
for queries involving distributed files, communications to remote systems
are done in a synchronous fashion.
The following example shows you how
to use the CHGQRYA command in combination with the Start Debug (STRDBG) command
to analyze a distributed query:
STRDBG UPDPROD(*YES)
CHGQRYA ASYNCJ(*NONE)
STRSQL
SELECT COUNT(*) FROM EMPLOYEE A
The following debug
messages are put into the job log:
Current connection is to relational database SYSA.
DDM job started.
Optimizer debug messages for distributed query step 1 of 2 follow:
Temporary distributed result file *QQTDF0001 built for query.
Following messages created on target system SYSB.
Arrival sequence access was used for file EMPLOYEE.
Arrival sequence access was used for file EMPLOYEE.
Optimizer debug messages for distributed query step 2 of 2 follow:
Arrival sequence access was used for file EMPLOYEE.
ODP created.
Blocking used for query.