Search

Top 60 Oracle Blogs

Recent comments

tcp

Oracle wait event ‘TCP Socket (KGAS)’

I was asked some time ago what the Oracle database event ‘TCP socket (KGAS)’ means. This blogpost is a deep dive into what this event times in Oracle database 12.1.0.2.180717.

This event is not normally seen, only when TCP connections are initiated from the database using packages like UTL_TCP, UTL_SMTP and the one used in this article, UTL_HTTP.

A very basic explanation is this event times the time that a database foreground session spends on TCP connection management and communicating over TCP, excluding client and database link (sqlnet) networking. If you trace the system calls, you see that mostly that is working with a (network) socket. Part of the code in the oracle database that is managing that, sits in the kernel code layer kgas, kernel generic (of which I am quite sure, and then my guess:) asynchronous services, which explains the naming of the event.

Performing in the cloud – network latency

To me, ‘cloud computing’ is renting a compute resource to perform a task. In order to use that compute resource, you need to instruct it to do something, which is typically done via the network. If the task the compute resource needs to fulfil is being an application server or being a client or both in the case of an application server that uses an Oracle database, the network latency between the client of the database and the database server is a critical property.

TCP Trace Analysis for NFS

How do we know where latency comes from when  there is a disparity in reported I/O latency on  the I/O subsystem and that of the latency reported on the  client box requesting the I/O.

For example if I have an Oracle database requesting I/O  and Oracle says an 8Kb request takes 50 ms yet the I/O storage subsystem says 8Kb I/Os are taking 1ms (averages) , then where does the 49  extra ms come from?

When the I/O subsystem is connected to Oracle via NFS  then there are a lot of layers that could be causing the extra latency.

Screen Shot 2013-08-23 at 1.35.20 PM

Where does the difference in latency come from between NFS Server and Oracle’s timing of pread?