6.4 Customizing Probes

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6 Performance Monitoring and Management : 6.4 Customizing Probes

PEM uses probes to retrieve statistics from a monitored server, database, operating system or agent. A probe is a scheduled event that returns a set of performance metrics about a specific monitored object. You can use the Probe Configuration dialog (shown in Figure 6.12) to specify when each probe is executed.
To review or modify the currently defined probes for each server and its underlying objects (e.g. databases, tables, etc.), right click on the object name in the tree control and select Probe Configuration from the context menu. You can also access the Probe Configuration dialog by highlighting an object name, and selecting Probe Configuration from the Management menu.
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The Probe Configuration dialog displays a list of the metrics that are collected for the selected node. The Probe Configuration dialog may also display information about probes that cannot be modified from the current node. If a probe cannot be modified from the current dialog, the background (the area behind the node name) is greyed-out; when highlighted, the status bar will display the node level from which the statistic may be configured.
System probes are the built-in probes provided by PEM, and are part of the PEM schema. These probes are differentiated in the Probes list of the Custom Probes dialog by a grey background. You may only modify the Enabled, Interval and Data retention fields of a system probe.
Modifying the system probe default values will change the behavior of the probe any time the probe executes, unless the change is overridden on the Probe Configuration dialog. For example, if you change the Interval field of the Database Statistics probe from 5 minutes to 30 minutes, then each time the Database Statistics probe is invoked, the new value (30 minutes) will be enforced, except on those servers where the interval has been modified on the Probe Configuration dialog.
User-defined probes are those probes created by users. Use the Custom Probes dialog (accessed through the Management menu) to modify a user-defined probe. You can modify the Enabled, Interval and Data retention fields of the Definition tab, the Unit and Graphable fields of each column on the Columns tab, the code provided in the Code tab, and the code definition on the Alternate Code tab of a user-defined probe if the Applies to any server? field for that probe was set to No.
You can use the PEM Custom Probes dialog to create a new probe or modify an existing probe. After creating or modifying a probe, you can use the PEM Chart Manager to incorporate the data gathered by custom probes into existing or new charts. To open the Custom Probes dialog, select the Custom Probes… option from the PEM client Management menu.
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Check the Show system probes? checkbox to display a list of the system probes in the Probes list panel. Highlight the name of a probe to display the probe properties on the tabs on the right side of the dialog.
Use the fields on the Definition tab (see Figure 6.13) to modify the definition of an existing probe or to specify the properties of a new probe:
Use the Name field to provide a name for a new probe.
Use the Collection method field to specify the probe type. Use the drop-down listbox to select:
SQL - the probe will gather information via a SQL statement.
WMI - the probe will gather information via a Windows Management Instrumentation extension.
Batch - the probe will use a command-script or shell-script to gather information.
Before creating a batch probe on a Linux system, you must modify the agent.cfg file, setting the allow_batch_probes parameter equal to true and restart the PEM agent. The agent.cfg file is located in /opt/PEM/agent/etc.
On 64-bit Windows systems, agent settings are stored in the registry. Before creating a batch probe, modify the registry entry for the AllowBatchProbes registry entry and restart the PEM agent. PEM registry entries are located in HKEY_LOCAL_MACHINE\\Software\\Wow6432Node\\EnterpriseDB\\PEM\\agent.
Please note that batch probes are platform-specific. If you specify a collection method of Batch, you must specify a platform type in the Platform field.
Use the Target type drop-down listbox to select the object type that the probe will monitor. Target type is disabled if Collection method is WMI.
Choose a radio button next to Enabled? to specify if the probe in enabled by default. Specify Yes to enable the probe by default, or No to specify that the probe is disabled by default.
Use the minutes and seconds selectors to the right of the Interval label to specify how often the probe will collect data.
Use the Data retention field to specify the number of days that gathered information will be retained in the probe's history table.
Use the radio buttons next to Applies to any server? to specify that the code on the Code tab will execute for every server version. If Applies to any server? is No, you may specify code for a specific server version on the Alternate Code tab. Applies to any server? is disabled when the Collection method is WMI.
Use the radio buttons next to Discard from history to specify if the server should create a history table for the probe. Select Yes to discard probe history, or No to retain the probe history in a table.
Use the Platform drop-down listbox to specify the type of platform that the probe will monitor. This field is enabled only when the Collection method is Batch.
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Use the fields on the Columns tab (see Figure 6.14) to define the columns in which the probe data will be stored:
Use the Name field to specify the column name.
Use the Column Type drop-down listbox to specify if the column is a Key column (a primary key) or a Non key column. Non-key columns are generally metric items (values that can be graphed).
Use the Data Type drop-down listbox to specify the type of data that will be stored in the column.
Use the Unit field to specify the unit of measure that applies to the metric stored in the column. This unit is displayed on the Y-Axis of a custom chart or a Capacity Manager chart. This is an optional field.
Use the Graphable drop-down listbox to specify that the defined metric may be graphed, and that the probe should be accessible from the Capacity Manager or Manage Charts dialogs.
Use the Is PIT drop-down listbox to specify if the metric should be stored by point-in-time.
Use the Calculate PIT drop-down listbox to specify that the server should calculate a point-in-time value for the metric data. Calculate PIT is disabled if Is PIT is Yes.
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Use the Code tab (see Figure 6.15) to specify the default code that will be executed by the probe:
If the probe is a SQL probe, you must specify the SQL SELECT statement invoked by the probe on the Code tab. The column names returned by the query must match the Internal Name specified on the Column tab. The number of columns returned by the query, as well as the column name, data type, etc. must match the information specified on the Columns tab.
If the probe is a batch probe, you must specify the shell or .bat script that will be invoked when the probe runs. The output of the script should be as follows:
The first line must contain the names of the columns provided on the Columns tab. Each column name should be separated by a tab (\t) character.
The number of columns specified in the Columns tab and their names, data type, etc. should match with the output of the script output.
If the probe is a WMI probe, you must specify the WMI query as a SELECT WMI query. The column name referenced in the SELECT statement should be same as the name of the corresponding column specified on the Column tab. The column names returned by the query must match the Internal Name specified on the Column tab. The number of columns returned by the query, as well as the column name, data type, etc. must match the information specified on the Columns tab.
If Applies to any server version? (on the Definition tab) is set to Yes, the fields on the Alternate Code tab (see Figure 6.16) are disabled; if Applies to any server version? is No, you may provide version specific probe definitions on the Alternate Code tab.
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Code provided on the Alternate Code tab will execute when the probe is invoked on the specified database version:
Use the checkboxes in the Supported database versions box to select the database version(s) on which the alternate code definition will apply.
When the definition is complete, click the Add button to add the probe definition to the list at the top of the Alternate Code tab. To remove a probe definition from the list, highlight the list entry, and click the Remove button.
Please Note: If you select a database version, and leave the alternate code value blank, the code specified on the Code tab will be invoked when the probe executes on a server that matches that version.
When you've finished defining or modifying a probe, click OK to save the definition, or Cancel to exit the dialog without preserving your changes.

6 Performance Monitoring and Management : 6.4 Customizing Probes

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