Details for IBM Db2 Analytics Accelerator for z/OS Version 7.1.5 Release Notes

Please find information about new functions here .

General recommendations

• Under a very high system load, the accelerator might appear slow or run into timeouts.

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

• Do not use partial reload for replicated tables.

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.

• Multi-row inserts fail for rows containing a NULL value for columns with data type BINARY or VARBINARY.

  Recommendation
  Do not use the multi-row insert method for affected rows.

Queries

• Queries are not routed to a newly paired accelerator if they are submitted 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 before you route queries to a newly paired accelerator.

• Queries can return incorrect results if a query specifies a value greater than 0.0 for CURRENT QUERY ACCELERATION WAITFORDATA and
  1. There are more than 17 unique tables referenced in the query, i.e. more than 17 DBID/OBID pairs and
  2. When a LOAD operation has just completed on one of the replicated tables referenced in the query.
  or a query does not specify CURRENT QUERY ACCELERATION WAITFORDATA or specifies a value of 0.0 for CURRENT QUERY ACCELERATION WAITFORDATA and
  1. There are more than 17 unique tables referenced in the query, i.e. more than 17 DBID/OBID pairs and
  2. At least one referenced table is enabled for replication, or at least one referenced table switches from a loaded state to remove in progress.
• Queries return with error SQLCODE = -181, SQLSTATE = 22007 when the timestamp format yyyy-mm-dd-hh:mm:ss is used in the query.

  Recommendation
  Use a different supported time stamp format.

Loading tables

• Data on an accelerator might be uncompressed or the compression rate is lower than the rate used by Db2 for z/OS.

  This will be fixed in an upcoming release.

• After running the REORG utility in Db2 12 for z/OS,  reloads might be wrongly recommended for partitions that have already been loaded on the accelerator.

  Recommendation
  To receive correct reload recommendations, do not use interactive load recommendations and batch job change detection at the same time.

• Add-tables-jobs fail, and no clean-up job is started thereafter.
  When SYSPROC.ACCEL_ADD_TABLES ends abnormally, and is rerun after a few seconds, the following error message is returned:
  "AQT10050E: An internal error occurred on the <accelerator> accelerator: The table <table-name> was already added to the database system with location name <location-name>. The table cannot be added again."
  A subsequent call of SYSPROC.ACCEL_GET_TABLES_INFO returns the message:
  "AQT10134E: The <table-name> table does not exist on the <accelerator> accelerator."
  Recommendation
  Remove the table from the accelerator and add it again.

• Invoking SYSPROC.ACCEL_LOAD_TABLES repeatedly and without interruption on a table partitioned by growth or by range might cause the table to grow. The reason is that data in old, replaced versions of the reloaded partitions cannot be deleted fast enough.
  Recommendation
  If a partitioned accelerator-shadow table grows more quickly than the table usually grows in Db2 for z/OS, try to reload the partitions of that table less often.

• The stored procedure SYSPROC.ACCEL_LOAD_TABLES reports a data size twice as high as the amount that has actually been transferred.

• A load table operation is canceled with the following error message: The current transaction has been rolled back because of a deadlock or timeout. Reason code "68".
  Recommendation
  Restart the load operation.

• The load operation fails with message AQT20113E: Operation RECEIVE, which was supposed to transfer 4 bytes on TCP/IP socket 2, failed because the connection to the remote machine at IP address is unknown and port 0 has been closed unexpectedly. Reason: errno = 1121 (EDC8121I Connection reset.).
  Recommendation
  Repeat the load operation. If the problem reoccurs, restart the accelerator server from the IBM Db2 Analytics Accelerator Console. If the problem persists, open a service request and provide a trace file.

• Load operation fails -902 RowTableEvaluator error.

  Recommendation
  Retry the load.

• When running ACCEL_LOAD_TABLES and specifying lockMode="TABLESET", the operation may fail with AQT10071E.
  This error occurs when the state of an accelerator table prohibits a certain type of operation. For the SYSPROC.ACCEL_SET_TABLES_ACCELERATION(ON) operation, the allowed states are Loaded and UpdateInProgress.

  Recommendation
  Remove the previous load and re-run the LOAD operation.

Incremental updates

• If it takes a long time to reload a set of incrementally updated tables, incremental update processing also takes longer and the replication latency increases. 
  Recommendation
  Pause after each reload, as this allows the system to come back to normal throughput rates and latency levels.
   

• Network issues or component failures might lead to an interruption of incremental update processes. In such a situation, it can happen that the log reader position, as reported by the CDC capture agent, does not advance anymore. Moreover, the replication counters reported by the SYSPROC.ACCEL_GET_ACCELERATOR_INFO stored procedure do not increase any further.
  Recommendation
  Stop affected incremental update processes. Then restart these.

• If incremental updates are enabled for an accelerator, the start of any new task might fail with an error message like:
  "DRDATCPIPException: A TCP operation timed out on message type 0x0000: Receive message failed after timeout of 10 seconds" is received.

  Recommendation
  Restart the task.

• Incremental updates stop unexpectedly.  If you run the getReplicationEvents function of the SYSPROC.ACCEL_CONTROL_ACCELERATOR stored procedure, the following events are reported:
  Type: Error
  Event ID: 1,475
  Originator: com.datamirror.ts.target.apply.bulkapply.db2.Db2TargetBulkApplyJob
  Time: Oct 15, 2018, 9:55:28 PM
  Message:
  Subscription <subscriptionname> is terminating abnormally.
  
  Type: Error
  Event ID: 6,702
  Originator: com.datamirror.ts.target.apply.bulkapply.ExecuteBulkApplyStatementJob
  Time: Oct 15, 2018, 9:55:28 PM
  Message:
  Mirror bulk apply operation failed.
  A SQL exception has occurred. The SQL error code is '0'. The SQL state is: [null]. The error message is: Mirror bulk apply external table insert error occurred. Actual number of affected rows (...) are not equal to expected number of affected rows (...).

  Recommendation
  Disable replication for the affected tables. Then re-enable replication for these tables and reload them.

• In a mixed version 5/version 7 environment (Capture Agent is shared by a version 5 and a version 7 environment), a replication status of "Error" is reported. A restart of the Capture Agent does not resolve the error state for the version 7 environment.

  Recommendation
  Restart incremental update processes from the Db2 Analytics Accelerator Console.

• If replication stops and restarts unexpectedly WAITFORDATA queries may be unexpectedly answered with rsn=1:Table(s) are in invalid state.

  Recommendation
  Stop replication via ACCEL_CONTROL_ACCELERATOR(stopReplication) and start replication again via ACCEL_CONTROL_ACCELERATOR(startReplication)

Monitoring

• The table size shown for each table in the accelerator view of the IBM Db2 Analytics Accelerator Studio is too large.
• The table-level statistics displayed in the IBM Db2 Analytics Accelerator Studio is incorrect. Table sizes statistics do not reflect the actual usage on the accelerator. For example, the table size metrics do not reduce when data is deleted from the table.

  However, the total space usage on the accelerator (Q8STDSA / Q8STDSKB) is correct.

• The value for the monitoring counter Q8STTMUD are to high, e.g. 0.18E+20.

  Recommendation
  The high value can be ignored. It will be corrected during the next statistics collection.

Stored procedures

• If applications call a IBM DB2 Analytics Accelerator for z/OS stored procedure without fetching the trace result set, e.g. the provided sample program SAQTSAMP(AQTSCALL), the trace file of the stored procedure is always kept on disk. This happens although the traceConfig specification in the MESSAGE parameter indicates a removal of the trace file.

  Recommendation
  Inspect the trace file location for obsolete older trace files (per default of name pattern aqt-trace-*) and remove them.

Miscellaneous

• 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 or queries.
  Symptoms are aborted tasks, lock timeout exceptions, or messages with SQL code -911 and SQLSTATE=40001 and rc=68.

  Recommendation
  Reduce the task diversity of parallel jobs if you process big table sets with more than 10000 tables. For example, do not run 'Alter Keys', 'Add Tables', and 'Remove Tables' operations at the same time. Reduce this to 'Alter Keys' and 'Add Tables' jobs or any other combination of just two different tasks.
  If a query failed, rerun the query.

• Under a high system load with a high memory usage, the database engine of the accelerator might be restarted automatically, which leads to the abortion of running queries.

  Recommendation
  Restart the aborted tasks and queries.

Issues specific to IBM Db2 Analytics Accelerator on IBM Z

• IDAA on Z query performance below customer expectation in large memory configuration.

  Recommendation
  Contact IBM to get support with memory configuration and reload recommendation.

• When using an 'EXCEPT ALL' clause for queries executed on the accelerator the query result is incorrect because duplicated values are handled incorrectly.

  Recommendation
  Avoid using an 'EXCEPT ALL' clause in queries executed on the accelerator.

Restrictions

• 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

• After clicking on "Apply" in Datastudio to start a software update operation, no pop up window is displayed to indicate that the software update has been started.

  Recommendation
  If this window does not come up shortly after clicking the button, click the button again.