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IBM Db2 Analytics Accelerator for z/OS Version 7.1.3 Release Notes

Release Notes


Abstract

This document describes enhancements and fixes in IBM Db2 Analytics Accelerator for z/OS Version 7.1.3.

Content

What's new

  • Further performance improvements for load jobs, queries, and incremental updates
  • Query support for the BINARY, ROWID and DECFLOAT data types also in connection with Db2 12 for z/OS
  • Recursive SQL support

Known issues and restrictions

Known issues and restrictions in earlier releases are resolved if they are not listed 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.

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

  • 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.

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.

  • Tables remain in state 'LOAD IN PROGRESS' after loading has ended.
    Recommendation
    Remove the affected tables from the accelerator and add them again.

 

Incremental updates

  • If it takes a long time to reload multiple incrementally updated tables, the overall throughput of incremental updates and the replication latency might be impacted negatively.
    Recommendation
    Pause after each reload, as this allows the system to come back to normal throughput rates and latency levels.
     
  • In rare situations, incremental updates stop and the spooled output of CHCPROC shows the following error message:
    CHC7061E Failure in TCP/IP send. The returned errno is ECONNRESET for a value of 54

    Recommendation
    On the Db2 Analytics Accelerator Console, select "Restart Incremental Update processes".

  • 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.

Miscellaneous

  • 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 in IBM Db2 Analytics Accelerator Studio 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 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

Query

  • The accelerator goes offline when many parallel queries produce a high workload.
    The system log shows the following message: "Accelerator is not online", "System went from state 'ONLINE' to 'UNKNOWN'

    Recommendation
    After some time, the accelerator restarts its services and goes online again. Then rerun the affected queries.

Topology limitations

  • A gateway can only be specified for one of the defined network interfaces, which then becomes the default route for the system. An interface without a gateway is accessible only from systems that belong to the the same subnet as the 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.

Document information

More support for: DB2 Analytics Accelerator for z/OS

Software version: 7.1.0

Operating system(s): z/OS

Reference #: 0716267

Modified date: 20 September 2018


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