Symptoms

Some process tasks which should execute powershell script do not actually execute it. Attributes do not get provisioned to target systems (Active Directory / Exchange) anymore. Nothing has changed in the configuration to cause this and similar setup in our other environment works
Error from OIM logs:

<Error> <ORACLE.IAM.CONNECTORS.ICFCOMMON.CONNECTOROPHELPER> <BEA-000000> <oracle.iam.connectors.icfcommon.ConnectorOpHelper : execute : Error occured while executing action
 java.lang.RuntimeException: The file exists.  ...

Error from ".NET" connector-server logs:

ConnectorServer.exe        Error       0             The file exists.  
 at Org.IdentityConnectors.Framework.Impl.Api.Remote.Messages.OperationResponsePart ProcessOperationRequest(Org.IdentityConnectors.Framework.Impl.Api.Remote.Messages.OperationRequest) in Server.cs:609
 ...

Solution

"The file exists" error is related to .NET. The error gets thrown when %temp% directory exceeds 65535 files. To solve this issue you should delete all temp files from %temp% directory for the user running the connector-service. For example "C:UsersOimServiceUserAppDataLocalTemp". Seems the connector-server makes use of some temporary files for powershell script execution and does not clean up afterwards.