Make sure that the Replicator Service and any service needed for the control database (Db2 for LUW or SQL Server) are running on the computer that is managing the subscription, and that the source and destination DBMS are available. The topic Controlling Services for SQDR, Db2 for LUW and SQL Server describes how to review the status and start and stop Windows services.
If many replications use the same source or destination at the same time, check that the Maximum Number of Connections setting for each source and destination is large enough to accommodate the simultaneous replications. Once a given source or destination has the maximum number of connections in use, no new replication involving that source or destination will start until a connection becomes available or the connection limit is increased. Data Replicator will wait up to two hours for a source or destination connection for a replication, but if no connection becomes available in that time, the operation is canceled and an error is recorded in the Windows Event Log.
Make sure that your edition of SQL Server supports enough tasks for the number of simultaneous subscriptions and other tasks you need to run. Contact your Microsoft software provider or refer to the Microsoft SQL Server Web site (http://www.microsoft.com/sql/) for the specifications of the various editions.
If your replications involve Db2 sources or destinations, make sure that you are licensed for an adequate number of StarSQL connections. To decrease the possibility that idle pooled connections may prevent Data Replicator from establishing active connections to other sources or destinations, you can reduce the Time Limit setting on the Connection Pools tab of the Service Properties dialog box, and you can reduce Maximum Connection Pool Size settings for the source and destination. Contact Stelo if you need to purchase additional licenses.