DTM and GTM in the same site

I second the notion that having more than 1 TMS on a site is not generally a good idea.  However if you are forced down this path there are a few things to make sure you are doing / not doing.

1) NEVER EVER EVER use one TMS to deploy another TMS.  It's bad mojo.

2) The success rate of having code in one TMS try to grab variables that are being set/used in the other TMS will be quite low and it most likely not something any TMS vendor will support.

There might be other items but these are the 2 that stand out the most to me.

Hi Jantzen,

My question is just to confirm something. I don't intend to add two TMS in the same site but I need to see other opinions about this topic. DTM is not very popular in Brazil, so I thought I'd better ask.

Understood. Did you have other questions about DTM that we could help with? If not, could you mark one of the replies as the correct answer?

Hello! I have a similar question, and would like to fully understand key disadvantages of having both GTM and DTM on the same site. Site speed? Inconsistency in data? Any other reasons not to have both running at the same time? Would appreciate any references to official sources where this can be outlined. Thank you in advance! 

Rudi pointed out a few of them above:

• Deploying one tag manager using another won't ever be supported and can lead to unreliable deployments
• Success rates of having one tag manager interact with another will be unreliable at best
• The more you have running/loading on your page, the slower it will load. If you're loading two tag managers, you're doing everything twice.
• Data will likely not match since different tools and tag management systems will have different methods of collecting and sending data
• ect...

Is there a specific reason you want to deploy both on the same site? DTM is able to deploy any pixel/code you'd like. Almost all limitations of DTM are being addressed with Adobe's newest tag management offering Launch, by Adobe

Thank you Jantzen. Agreed with everything mentioned here. The main reason for deploying both is related to media tracking and Google Adwords integration. The client wants to continue using AdWords, and I've heard Adobe's integration with it isn't perfect...

Sounds like a great opportunity for someone to write a "perfect" extension in launch for the integration.

Launch is being built as an open platform where customers and third-party consultants will be able to build their own extension. This will allow for our experts within the community to build integrations with just about any pixel/tag out there. We will no longer be limited by having a single team being responsible for every integration and extension.