The nzds command

Use the nzds command to manage and obtain information about the data slices in the system.

Syntax

The nzds command has the following syntax:
 nzds [-h|-rev] [-hc] subcmd [subcmd_options]

Inputs

The nzds command takes the following inputs:
Table 1. The nzds input options
Input Description
nzds show [options] Displays information about the data slice topology. The show subcommand is the default and displays a list of all the data slices on the system and information about status, the SPU that manages the data slice, the Primary Storage (that is, the disk ID where the primary copy of the data slice resides), the Mirror Storage (that is, the disk ID where the mirror copy of the data slice resides), and % Used (the amount of space in the data slice that contains data).

You can specify one or more options to show specific output.

nzds show [-detail] Displays information about the data slice topology and includes information about locations and disk space.
nzds show -spa id Displays information about the data slices which are owned by a particular S-Blade in the SPA.
nzds show -dsId id Displays information about the specific data slice.
nzds show -id hwId Displays information about the data slices that are assigned to the specified hardware.
nzds show -topology Displays the current storage topology. The output shows how system resources such as SPUs, disks, SAS switches, and HBA ports are used within the system to support the storage paths. This command is not supported on IBM® Netezza® High Capacity Appliance C1000 systems or on Netezza Platform Development Software.
nzds show -caCertFile path Specifies the path name of the root CA certificate file on the client system. This argument is used by clients who use peer authentication to verify the Netezza Performance Server host system. The default value is NULL, which skips the peer authentication process.
nzds show -securityLevel level Specifies the security level that you want to use for the session. This option does not apply when you are logged in to the Netezza Performance Server system and running the command. The argument has four values:
preferredUnSecured
This value is the default value. Specify this option when you would prefer an unsecured connection, but you accept a secured connection if the Netezza Performance Server system requires one.
preferredSecured
Specify this option when you want a secured connection to the Netezza Performance Server system, but you accept an unsecured connection if the Netezza Performance Server system is configured to use only unsecured connections.
onlyUnSecured
Specify this option when you want an unsecured connection to the Netezza Performance Server system. If the Netezza Performance Server system requires a secured connection, the connection is rejected.
onlySecured
Specify this option when you want a secured connection to the Netezza Performance Server system. If the Netezza Performance Server system accepts only unsecured connections, or if you are attempting to connect to a Netezza Performance Server system that is running a release before 4.5, the connection is rejected.
nzds show -regenStatus [-detail] Displays information about the status of any disk regenerations that are in progress. The command displays information about the Data Slice being regenerated, its SPU owner, the Source data slice ID, its Destination data slice ID, the Start Time of the regeneration, and % Done.

Include the -detail option for more information such as the locations of the SPUs and storage areas.

The regenStatus takes time to reflect as this is proportional to the amount of user data loaded on the system and number of data slices being regenerated on an individual SPU (~ 30 minutes).

nzds show -issues [-detail] Displays information about data slices that are reporting problems. The command displays a list of data slices to investigate and their Status, SPU, Primary Storage, Mirror Storage, and % Used.

Include the -detail option for more information such as location details and data slice size.

Note: The size of the data slice is reported in gibibytes, which is in units of 10243 bytes.
nzds rebalance

nzds has a new subcommand rebalance. Each data slice is "owned" by an SPU node that services query snippets against that data slice. The content of a data slice (subsets of rows from user tables in the system) is stored on a primary copy and a mirror copy. Under normal circumstances, the primary copy of a data slice is stored on a disk that is locally attached to the SPU that owns the data slice, which is ideal for query performance. After one or more disk or SPU failovers and or activations, it is possible for some data slices to become "remote", in that the primary copy of a data slice is on a disk that is not local to the SPU that owns the data slice. In addition, the distribution of primary data slices copies across disks and SPUs can become unbalanced.

Both of the above degrade query performance, which can be improved by running the nzds rebalance command. This command makes the SPU that holds (on one of its disks) the primary copy of a data slice the owner of that data slice. Additionally, nzds rebalance regenerates some primary data slice copies on different SPUs to achieve better balancing. If any rebalancing of either kind is needed, this command causes a system state change (from Online through Pausing (Now) and Discovering to Online again), which interrupts ongoing SQL queries and transactions.

After multiple hardware failovers, nzds rebalance can take more than one iteration to bring the system into a balanced state. It is advised to observe the output of the nzds rebalance -check command and perform rebalance accordingly.

Options

The nzds command takes the following options:
Table 2. The nzds options
Option Description
-host hostname Specifies the host name or IP address of the Netezza Performance Server system.
-u user Specifies the database user name [NZ_USER].
-pw password Specifies the user password [NZ_PASSWORD].
-timeout secs Specifies the amount of time in seconds to wait for the command to complete before it exits with a timeout error. Default is 300.

Description

The nzds command has the following description:
Privileges required
Your database user account does not require any special administrative privileges to run the nzds show command.
Common tasks
Use the nzds command to manage and display information about the data slices in the system. You can also use this command to create a balanced topology for best performance of the system.

Usage

The following provides some sample usage:
  • To show information about regenerations that are in progress:
    nzds show -regenstatus
    Data Slice SPU  Source Destination Start Time              % Done
    ---------- ---- ------ ----------- ----------------------- --------
    5          1092 1035   1014        09-Apr-09, 07:24:55 EDT 0.01
    6          1092 1035   1014        09-Apr-09, 07:24:55 EDT 0.01
  • To show the data slice information for the system, use the following command:
    nzds show 
    Data Slice Status  SPU  Partition Size (GiB) % Used Supporting
    Disks
    ---------- ------- ---- --------- ---------- ------ ---------------
    1          Healthy 1017 2         356        58.54  1021,1029
    2          Healthy 1017 3         356        58.54  1021,1029
    ...

    The sample output that is shown for this command is truncated for the documentation.

  • To show the data slice issues reported for the system, use the following command:
    nzds show -issues
    Data Slice Status   SPU  Partition Size (GiB) % Used Supporting Disks
    ---------- -------- ---- --------- ---------- ------ ----------------
    11         Degraded 1113 4         356        11.80  1091
    12         Degraded 1113 5         356        11.79  1091
  • To change the system state, run the following command:
    nzds rebalance
    This operation causes system state change. Are you sure you want to proceed (y|n)? [n]