Sitecore xDB Analytics Rewrite Sync Token Issue

This issue is to do with Sitecore xConnect Search service unable to rewrite the sync token issue for the following two reasons:

• Core database shared with more than one Sitecore instance. This can be a potential problem as most developers may share the core database between their local and development environment.
• Missing Solr aliases to both the xdb collection and xdb rebuild collection when configuring Solr provider to use SolrCloud.

In order to address this issue, the following prerequisites apply:

• Configure the Solr Provider for xConnect
  https://doc.sitecore.com/developers/90/platform-administration-and-architecture/en/configure-the-solr-search-provider-425248.html
• Two xConnect Solr cores: the live core (usually xdb) and the rebuild core, which has a _rebuild suffix (like xdb_rebuild) are created.
• Both cores are based on the basic_configs file.
• xConnect schema modifications have been applied to both cores
  https://doc.sitecore.com/developers/90/sitecore-experience-platform/en/rebuild-the-xdb-index-in-solr.html
• Ensure xConnect connectionstrings are connected to SolrCloud

Steps to fix:

1. Remove your old xdb and xdb_rebuild collections
2. Create new xdb and xdb_rebuild collections
3. Apply xDB schema modifications to both  new collections created in 2). See this page for more information.
4. Create two aliases and associate them with the two following xDB collections respectively. Please make sure to check  that your aliases are pointing correctly to your xDB collections by browsing to https://%5Byoursolrinstancedomain%5D/solr/admin/collections?action=LISTALIASES
   • xdb
   • xdb_rebuild
5. Specify the solrCore connection string with the name of the new xdb collection attached to Solr in these configuration files:
   • xconnect\App_Config\ConnectionStrings.config
   • xconnect\App_data\jobs\continuous\IndexWorker\App_config\ConnectionStrings.config
6. Restart the xConnect App Service
7. Rebuild the xDB Solr Index by following the steps outlined in the article below:
   • The last one I wanted to mention was the place to run “.\XConnectSearchIndexer.exe -rr” in the terminal. Please ensure to run it under this path: “D:\local\Temp\jobs\continuous\IndexWorker[WORKING]”. More details can be found here: https://doc.sitecore.com/developers/91/sitecore-experience-platform/en/rebuild-the-xdb-index-in-azure-search.html (Although this page says Azure Search, however since it’s Azure Search, this assumes the context of Sitecore being hosted in Azure PaaS, where the other Solr documentation page is assuming on a Windows Server hosting)

Article Walkthrough:

https://doc.sitecore.com/developers/91/platform-administration-and-architecture/en/walkthrough–using-solrcloud-for-xconnect-search.html

I hope this article will help you resolve something which I spent about a few days trying to figure out. 🙂