IBM DB2 Analytics Accelerator for z/OS Version V7.1.1 Release Notes

General recommendations

• Under very high load the accelerator may appear slow or might run into timeouts.

  Recommendation
  Do not run more than 30 load threads in parallel.

Creating accelerator-only tables

• Creating an accelerator-only table fails with a message indicating that the accelerator-only table is not available.

  Recommendation
  Retry the operation.

Queries

• A query runs for hours while the reload of a referenced table is in progress.

  Recommendation
  Cancel the query and wait until table statistics have been generated for new or reloaded tables.

• Queries might not be routed to a newly paired accelerator shortly after the pairing.
  THE STATEMENT CANNOT BE EXECUTED BY DB2 OR IN THE ACCELERATOR (REASON 13). SQLCODE=-4742, SQLSTATE=560D5, DRIVER ...

  Recommendation
  Wait 30 seconds after pairing a new subsystem with an accelerator before you route queries to it.

• Queries do not return results after the following sequence of events:
  
  • The reload of a table with the option forceFullReload=true
  • The termination of the load process through task cancellation
  • A reload of the same table with the option forceFullReload=false

  Recommendation
  Remove the affected table from the accelerator and add it again.

• Under a very high system load, the accelerator status may be erroneously reported as 'offline' by the monitoring tools or in DSNX870I / DSNX881I messages, and new queries are, depending on your configuration, either executed in Db2 or aborted with SQLCODE=-4742, RC=13.

  Recommendation
  Restart the affected queries.

Loading tables

• If the SYSPROC.ACCEL_LOAD_TABLES stored procedure has been called by an external loader (such as the Db2 Analytics Accelerator Loader for z/OS), the procedure might report a successful job completion for accelerator-only tables although no data has been loaded.

  Recommendation
  This is a current restriction that will be removed in the near future.

• The stored procedure SYSPROC.ACCEL_LOAD_TABLES might fail with the message:
  "DSNT408I SQLCODE = -913, ERROR: UNSUCCESSFUL EXECUTION CAUSED BY DEADLOCK OR TIMEOUT. REASON CODE 00C9008E.

  Recommendation
  Repeat the load operation.
  If the problem persists, check the list of product prerequisites. Ensure that the Db2 for z/OS PTFs UI54612 and UI54615 are installed.

Monitoring

• An incorrect table size is shown in IBM Db2 Analytics Accelerator Studio and IFI records.

Tracing

• If an accelerator is restarted during a table load, very large trace files are created. As a consequence, the collection of trace information takes a long time.

  Recommendation
  Do not restart an accelerator while the stored procedure SYSPROC.ACCEL_LOAD_TABLES is running.

Miscellaneous

• Stored procedures threads are not cancelled after closing IBM Db2 Analytics Accelerator Studio.

  The -DISPLAY THREAD command on the z/OS console shows active threads although IBM Db2 Analytics Accelerator Studio has been closed.

• The accelerator server might crash if it is shut down while asynchronous load operations are running. Symptoms: the server is restarted and a core dump is created.

  Recommendation
  Do not shut down the server from the Db2 Analytics Accelerator Console as long as asynchronous load operations are running. (Check this with the List tasks function before.)

• Under a very high system load caused by the parallel execution of various operations, such as 'Add Tables', 'Remove Tables', and 'Alter Keys', the accelerator might restart unexpectedly, leading to the abortion of running tasks.

  Recommendation
  Do not run 'Alter Keys' operations at the same time as 'Add Tables' or 'Remove Tables' operations if you process big table sets that affect more than 10000 tables.

Issues specific to IBM Db2 Analytics Accelerator on IBM Z

Query

• The accelerator terminates connections and ultimately reboots if the query workload is too high.

  Recommendation
  If the accelerator does not recover within several minutes, restart the accelerator from IBM Db2 Analytics Accelerator Studio.

• The accelerator goes offline when many queries are running in parallel and produce a high workload.
  System log shows: "Accelerator is not online", "System went from state 'ONLINE' to 'UNKNOWN'

  Recommendation
  After some time, the Accelerator will restart services and come online again. Then rerun the affected queries.

Restrictions

• A gateway can only be specified for one of the defined network interfaces, which then becomes the default route for the system. An interface that does not have a gateway set is only accessible from systems on the same subnet as that interface.

  Recommendation
  Use a single gateway definition for a router and connect Db2 subsystems in different subnets to this router.

• The accelerator does not support a combination of FICON DASD and FCP storage devices within the same storage pool.

  Recommendation
  Use only FICON DASD or only FCP storage devices for a specific storage pool definition.

Issues specific to IBM Db2 Analytics Accelerator Studio

• A refresh of the accelerator view takes very long after adding a very high number of tables in a short time.