Issue : All virtual circuits are in use

Database
Teradata Employee

Issue : All virtual circuits are in use

Hi All,

We are facing issue “All virtual circuits are in use”. I know this issue comes when we have reached the session limit either in PE or gateway. Can anybody tell what the limit for gateway is as PE can handle 120 sessions

and we have 2 Node (4 PE) that means it can handle 4*120=480 sessions. When we got this issue there were only aprox. 190 sessions. So it may be the case for gateway.

Would it be good to connect with different IP for this system as we all are using one IP to connect this system? If yes please explain.

As we are able to check that all PE are having almost same number of sessions.

Please suggest resolving this issue.

16 REPLIES
Junior Supporter

Re: Issue : All virtual circuits are in use

Hi.

Speaking from memory:

Gateway can handle up to 1200 connections, 600 is the default though.

Cheers.

Carlos.

Teradata Employee

Re: Issue : All virtual circuits are in use

Thanks Carlos for your reply.

but sessions are not that much. But still we are facing this issue.

Then what may be the reason. It wiil be great help if you provide some input for this.

Junior Supporter

Re: Issue : All virtual circuits are in use

Hi

Check the value of the sessions allowed in the gateway configuration with gtwcontrol utility.

Cheers.

Carlos

Teradata Employee

Re: Issue : All virtual circuits are in use

Its 600.

Junior Supporter

Re: Issue : All virtual circuits are in use

Hi

I overlooked this:

"Would it be good to connect with different IP for this system as we all are using one IP to connect this system? If yes please explain."

If the connections are made with explicit IPs instead of using 'Cop' entries you may be flooding one node/PE/Gateway.

Cheers.

Carlos.

Teradata Employee

Re: Issue : All virtual circuits are in use

Thanks Carlos

It means that connection with one IP connect to the PEs on that Node only ?

BUT

I found that each PE has equall number of sessions ,with the help of logonoff view. It means that sessions connect with one IP but these sesssions are being divided among all the PEs for load balancing internally ( i do not know how its happening)

One thing i know about Cop Entry that if one node is down and HSN comes then users will not know which IP they are connect now, means users will not affect. it help to balance the sessions in between IPs of different Nodes.

Please suggest and correct if i am wrong.

Junior Supporter

Re: Issue : All virtual circuits are in use

Hi.

The gateway distributes the requests from workstations to the PEs on the same node where the gateway is running.

Cheers.

Carlos.

Teradata Employee

Re: Issue : All virtual circuits are in use

@Sandeep,

Regarding: "It means that connection with one IP connect to the PEs on that Node only ?"

The answer is No. The way it works is that connections is one IP address connect to Teradata Database Gateways on that node only. TCP connections go to Teradata Database Gateways; they do not go to PEs directly.

@Carlos,

Regarding: "The gateway distributes the requests from workstations to the PEs on the same node where the gateway is running."

First, I suspect that when you used the word "requests", you actually meant "session logon requests".

So if we modify your statement to "The gateway distributes the session logon requests from workstations to the PEs on the same node where the gateway is running."

Actually, that's not true. The Teradata Database Gateway distributes each session logon request to the PE with the fewest number of logged-on sessions, and that PE may be on the same node as the Gateway, or it may be on a different node from the Gateway.

Teradata Employee

Re: Issue : All virtual circuits are in use

And by the way, a few years back I created an RFC against the Teradata Database Gateway -- GTW RFC 138835 "At logon time DBS Gateway should prefer On-Node PE for the session"

That RFC is planned to be included in an upcoming release of the Teradata Database.

Even after that RFC ships; however, it will still be possible for the Gateway to select a PE for a session that is on a different node from the Gateway. What that RFC does is change the Gateway's algorithm for choosing a session's PE such that it will try to select an on-node PE when it can.