anchor.diff:  
   5. Restart PXF on each Greenplum Database segment host as described in [Restarting PXF](cfginitstart_pxf.html#restart_pxf).
   
  +
   ## <a id="pxf-timezonecfg"></a>Addressing PXF JDBC Connector Time Zone Errors
   
   You use the PXF JDBC connector to access data stored in an external SQL database. Depending upon the JDBC driver, the driver may return an error if there is a mismatch between the default time zone set for the PXF server and the time zone set for the external SQL database.
  
positive.code: 
  ## <a id="pxf-memcfg"></a>Addressing PXF Memory Issues
  
  Because a single PXF agent (JVM) serves multiple segments on a segment host, the PXF heap size can be a limiting runtime factor. This will be more evident under concurrent workloads and/or queries against large files. You may run into situations where a query will hang or fail due to insufficient memory or the Java garbage collector impacting response times. To avert or remedy these situations, first try increasing the Java maximum heap size or decreasing the Tomcat maximum number of threads, depending upon what works best for your system configuration.
  
  **Note**: The configuration changes described in this topic require modifying config files on *each* node in your Greenplum Database cluster. After you perform the updates on the master, be sure to synchronize the PXF configuration to the Greenplum Database cluster.
  
  You will need to re-apply these configuration changes after any PXF version upgrades.
  
  ### <a id="pxf-heapcfg"></a>Increasing the JVM Memory for PXF
  
  Each PXF agent running on a segment host is configured with a default maximum Java heap size of 2GB and an initial heap size of 1GB. If the segment hosts in your Greenplum Database cluster have an ample amount of memory, try increasing the maximum heap size to a value between 3-4GB. Set the initial and maximum heap size to the same value if possible.
  
  Perform the following procedure to increase the heap size for the PXF agent running on each segment host in your Greenplum Database cluster.
  
  1. Log in to your Greenplum Database master node:
  
      ``` shell
      $ ssh gpadmin@<gpmaster>
      ```
  
  2. Recall the location of the PXF user configuration directory (`$PXF_CONF`). Edit the `$PXF_CONF/conf/pxf-env.sh` file. For example:
  
      ``` shell
      gpadmin@gpmaster$ vi $PXF_CONF/conf/pxf-env.sh
      ```
  
  3. Locate the `PXF_JVM_OPTS` setting in the `pxf-env.sh` file, and update the `-Xmx` and/or `-Xms` options to the desired value. For example:
  
      ``` shell
      PXF_JVM_OPTS="-Xmx3g -Xms3g"
      ```
  
  
  3. Save the file and exit the editor.
  
  4. Use the `pxf cluster sync` command to copy the updated `pxf-env.sh` file to the Greenplum Database cluster. For example:
  
      ``` shell
      gpadmin@gpmaster$ $GPHOME/pxf/bin/pxf cluster sync
      ```
  
  5. Restart PXF on each Greenplum Database segment host as described in [Restarting PXF](cfginitstart_pxf.html#restart_pxf).
  
  ### <a id="pxf-threadcfg"></a>Another Option for Resource-Constrained PXF Segment Hosts
  
  If increasing the maximum heap size is not suitable for your Greenplum Database deployment, try decreasing the number of concurrent working threads configured for PXF's underlying Tomcat web application. A decrease in the number of running threads will prevent any PXF node from exhausting its memory, while ensuring that current queries run to completion (albeit a bit slower). Tomcat's default behavior is to queue requests until a thread is free, or the queue is exhausted.
  
  The Tomcat default maximum number of threads is 300. Decrease the maximum number of threads to a value that works optimally for your Greenplum Database deployment. (If you plan to run large workloads on a large number of files in an external Hive data store, specify an even lower value.)
  
  Perform the following procedure to decrease the maximum number of Tomcat threads for the PXF agent running on each segment host in your Greenplum Database deployment.
  
  1. Log in to your Greenplum Database master node:
  
  
negative.code:     $ ssh gpadmin@<gpmaster>
      ```
  
  2. Edit the `$PXF_CONF/conf/pxf-env.sh` file. For example:
  
      ``` shell
      gpadmin@gpmaster$ vi $PXF_CONF/conf/pxf-env.sh
  