USER MANUALS


ALTER SESSION Statement

Virtual DataPort includes an statement that allows users to update session properties.

The syntax of the command is the following:

ALTER SESSION SET <property:literal> = <value:literal>

To restore some property to its default value:

ALTER SESSION SET <property:literal> = NULL

At the moment, this statement only allows to set the property querytimeout, which allows users to specify the default query timeout for VQL queries. That is, the maximum time (in milliseconds) the Server will wait for a VQL command to finish. After this period, the Server will cancel the command.

ALTER SESSION SET 'querytimeout' = '10000'

All the clients that connect to Virtual DataPort via JDBC or ODBC establish a default timeout for queries. This statement allows to override the query timeout specified by the client application for all later queries in the user session. A value of 0 implies “unrestricted” execution time (see note below).

It is possible to query the current session querytimeout using the GETSESSION function:

SELECT GETSESSION('querytimeout') FROM DUAL()

In addition, you can change the timeout for a single query by adding the parameter 'QUERYTIMEOUT' = '<value>' to the CONTEXT clause of the query. See more about this in the section CONTEXT Clause of the VQL Guide.

Note

In addition to the querytimeout, VQL commands may be affected by other types of timeouts like transaction timeouts or the thread timeout. So a VQL command can be aborted by the VDP server before the query timeout expires even if the query timeout is set to 0 (unrestricted). The Resource Manager can also impose limits to the query timeout.

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