OpenX Tips

One of the most useful screens in the OpenX ad server is the zone probability page. There’s an incredible amount of information that you can get from this screen about what’s happening with regards to banner delivery in your zones, if you know how to understand the information presented.

What’s linked and active?

The most immediately obvious information on the zone probability screen is the list of all banners that are linked and active¹ in the zone. The fact that the zone probability screen only shows active banners can be useful, as it allows you to easily see the difference between banners that are active in the zone, and any banners that are merely linked to the zone, as shown on the linked banners screen.

The zone probability screen showing only one active linked banner.

The zone linked banners screen, showing two linked banners -- one of which is inactive.

What’s targeted and/or capped?

Any banner in OpenX can have delivery limitations or capping applied, to target the delivery of the banner to certain users of your website. However, targeting or capping not only applies to your users, it also applied to you when you are viewing your site. Sometimes, that means that when you view your own website, you won’t see some of the active banners linked to the zone!

As a result, it’s often important to know exactly which banners have targeting or capping applied. The zone probability screen makes seeing which banners in a zone are targeted or capped very easy.

The zone probability screen showing which banners are targeted and capped.

What’s the approximate probability of seeing a banner?

The probability column of the zone probability screen shows, as you would expect, the approximate probability of OpenX delivering each of the active banners that are linked to the zone.

The probabilities shown are only approximate as a result of delivery limitations and capping.

• When delivery limitations and capping rules are applied to Contract (Exclusive) and Remnant campaign banners, then the banners will usually be shown less often than the probability shown. This is because the delivery limitations and capping reduce the available inventory that the banners can be displayed in.
• The OpenX Maintenance Prioritization Engine has code to compensate for the effect of delivery limitations and capping rules that are applied to banners in Contract campaigns. However, in The Guru’s experience, this compensation often means that the probability values shown on the zone probability screen for Contract campaigns are often, well, rather odd. This is because banners that are very highly targeted² are given a very high probability — but because of the fact that during the banner delivery process, banners that cannot be displayed are discarded, and then the priority values are re-calibrated, this means that the un-targeted Contract campaign banners with apparently low probabilities on the zone probability screen actually end up with much higher probabilities after re-calibration.

Are Contract campaigns over-subscribed?

If you’ve read The Guru’s article on how the OpenX banner delivery process works, you will know that a banner from a Contract campaign may not deliver on every impression, in the event that the OpenX Maintenance Prioritization Engine has decided that not every impression is required to be used up to allow the Contract campaigns to meet their delivery targets.

The converse of this is that if you run Contract campaigns in a zone, and if almost every impression in the zone is being used by a Contract campaign, then it might be the case that there is not enough inventory in the zone for the Contract campaigns to meet their delivery targets — a condition known as the zone being “over-subscribed”.

You can easily identify this situation by looking at the probability of your Remnant campaign banners in the zone — in particular, look at your “guaranteed delivery” campaign banner. If the probability is zero (or very close to zero), then your Contract campaigns in the zone are using up all of the inventory (or almost all of it) — and so the Contract campaigns may not be delivering to contract. If you see this, you may want to investigate the linked Contract campaigns to inspect their delivery progress — you may need to take action and update the campaign if it is not delivering sufficiently quickly!

The zone probability screen showing a Contract campaign using almost all of the zone's inventory, which may indicate an over-subscribed zone.

1. A banner is considered to be active if it’s in a campaign that is currently active — that is, is within its start and end dates, if they are set, and has not been disabled due to the campaign meeting its delivery targets, again, if it has any. Additionally, the banner itself must be active within the campaign. [↩]
2. That is, targeted to a very small part of the total zone inventory. [↩]