This is the search log. Looks like it detects more than one version of jdbc driver, and caused some re-scan attempt. Also got some error like "stderr: The system cannot find the file specified."
12-12-2018 20:42:20.286 INFO SearchOrchestrator - Creating the search DAG.
12-12-2018 20:42:20.286 INFO SearchParser - PARSING: | dbxquery connection=Realtime query="select 1 from DUAL;"
12-12-2018 20:42:20.299 INFO ChunkedExternProcessor - Running process: "C:\Program Files\Splunk\etc\apps\splunk_app_db_connect\windows_x86_64\bin\command.bat" -Dlogback.configurationFile=..\config\command_logback.xml -DDBX_COMMAND_LOG_LEVEL=INFO -cp ..\jars\command.jar com.splunk.dbx.command.DbxQueryCommand
12-12-2018 20:42:20.319 ERROR ChunkedExternProcessor - stderr: The system cannot find the file specified.
12-12-2018 20:42:20.837 ERROR ChunkedExternProcessor - stderr: 20:42:20.829 10636@W1835906 [main] INFO c.splunk.dbx.utils.TrustManagerUtil - action=load_key_manager_succeed
12-12-2018 20:42:20.916 INFO ChunkedExternProcessor - Custom search command is a generating command.
12-12-2018 20:42:20.917 INFO DispatchThread - BatchMode: allowBatchMode: 1, conf(1): 1, timeline/Status buckets(0):0, realtime(0):0, report pipe empty(0):0, reqTimeOrder(0):0, summarize(0):0, statefulStreaming(0):0
12-12-2018 20:42:20.917 INFO DispatchThread - required fields list to add to remote search =
12-12-2018 20:42:20.917 INFO DispatchCommandProcessor - summaryHash=NS3d9d854163f8f07a summaryId=92AEC8C6-1713-4938-B895-2A465856DC0D_search_thunder_wu_NS3d9d854163f8f07a remoteSearch=
12-12-2018 20:42:20.971 ERROR ChunkedExternProcessor - stderr: 20:42:20.924 10636@W1835906 [main] WARN com.splunk.dbx.message.MessageEnum - action=initialize_resource_bundle_files error=Can't find bundle for base name Messages, locale en_US
12-12-2018 20:42:21.990 ERROR ChunkedExternProcessor - stderr: 20:42:21.593 10636@W1835906 [main] INFO c.s.d.s.driver.DriverServiceImpl - action=load_drivers multiple version drivers exist, 2 drivers found.
12-12-2018 20:42:21.990 ERROR ChunkedExternProcessor - stderr: 20:42:21.593 10636@W1835906 [main] INFO c.s.d.s.driver.DriverServiceImpl - driver name is com.splunk.dbx.service.driver.DelegatingDriver, select version 12.2, loaded from file ojdbc8.jar
12-12-2018 20:42:21.990 ERROR ChunkedExternProcessor - stderr: 20:42:21.595 10636@W1835906 [main] INFO c.s.d.s.driver.DriverServiceImpl - action=register_driver driver=oracle.jdbc.OracleDriver 12.2 succeeded
12-12-2018 20:42:21.990 ERROR ChunkedExternProcessor - stderr: 20:42:21.595 10636@W1835906 [main] INFO c.s.d.s.driver.DriverServiceImpl - action=load_drivers spent 93 ms to rescan all jdbc drivers
12-12-2018 20:42:21.990 ERROR ChunkedExternProcessor - stderr: 20:42:21.660 10636@W1835906 [main] INFO c.s.dbx.connector.ConnectorFactory - action=collect_connection_pool_metrics interval_in_seconds=60
12-12-2018 20:42:23.010 INFO SearchParser - PARSING: | dbxquery connection=Realtime query="select 1 from DUAL;"
12-12-2018 20:42:23.011 INFO ChunkedExternProcessor - Running process: "C:\Program Files\Splunk\etc\apps\splunk_app_db_connect\windows_x86_64\bin\command.bat" -Dlogback.configurationFile=..\config\command_logback.xml -DDBX_COMMAND_LOG_LEVEL=INFO -cp ..\jars\command.jar com.splunk.dbx.command.DbxQueryCommand
12-12-2018 20:42:23.030 ERROR ChunkedExternProcessor - stderr: The system cannot find the file specified.
12-12-2018 20:42:23.549 ERROR ChunkedExternProcessor - stderr: 20:42:23.516 11756@W1835906 [main] INFO c.splunk.dbx.utils.TrustManagerUtil - action=load_key_manager_succeed
12-12-2018 20:42:23.603 INFO ChunkedExternProcessor - Custom search command is a generating command.
12-12-2018 20:42:23.604 INFO AstOptimizer - SrchOptMetrics optimize_toJson=0.594
12-12-2018 20:42:23.618 ERROR ChunkedExternProcessor - stderr: 20:42:23.611 11756@W1835906 [main] WARN com.splunk.dbx.message.MessageEnum - action=initialize_resource_bundle_files error=Can't find bundle for base name Messages, locale en_US
12-12-2018 20:42:24.637 ERROR ChunkedExternProcessor - stderr: 20:42:24.241 11756@W1835906 [main] INFO c.s.d.s.driver.DriverServiceImpl - action=load_drivers multiple version drivers exist, 2 drivers found.
12-12-2018 20:42:24.637 ERROR ChunkedExternProcessor - stderr: 20:42:24.241 11756@W1835906 [main] INFO c.s.d.s.driver.DriverServiceImpl - driver name is com.splunk.dbx.service.driver.DelegatingDriver, select version 12.2, loaded from file ojdbc8.jar
12-12-2018 20:42:24.637 ERROR ChunkedExternProcessor - stderr: 20:42:24.242 11756@W1835906 [main] INFO c.s.d.s.driver.DriverServiceImpl - action=register_driver driver=oracle.jdbc.OracleDriver 12.2 succeeded
12-12-2018 20:42:24.637 ERROR ChunkedExternProcessor - stderr: 20:42:24.242 11756@W1835906 [main] INFO c.s.d.s.driver.DriverServiceImpl - action=load_drivers spent 78 ms to rescan all jdbc drivers
12-12-2018 20:42:24.637 ERROR ChunkedExternProcessor - stderr: 20:42:24.300 11756@W1835906 [main] INFO c.s.dbx.connector.ConnectorFactory - action=collect_connection_pool_metrics interval_in_seconds=60
12-12-2018 20:42:25.656 INFO SearchParser - PARSING: | dbxquery connection=Realtime query="select 1 from DUAL;"
12-12-2018 20:42:25.656 INFO ProjElim - Black listed processors=[addinfo]
12-12-2018 20:42:25.663 INFO AstOptimizer - SrchOptMetrics optimization=0.000
12-12-2018 20:42:25.663 INFO SearchPhaseGenerator - Optimized Search =| dbxquery connection=Realtime query="select 1 from DUAL;"
12-12-2018 20:42:25.663 INFO ParallelReducePolicy - Current Search Head doesn't have any usable peers to use.
12-12-2018 20:42:25.664 INFO PhaseNodeGenerationVisitor - User lacking run_multi_phased_searches, rolling back to 2-phase mode.
12-12-2018 20:42:25.664 INFO PhaseToPipelineVisitor - Phase Search = | dbxquery connection=Realtime query="select 1 from DUAL;"
12-12-2018 20:42:25.664 INFO SearchParser - PARSING: | dbxquery connection=Realtime query="select 1 from DUAL;"
12-12-2018 20:42:25.664 INFO ChunkedExternProcessor - Running process: "C:\Program Files\Splunk\etc\apps\splunk_app_db_connect\windows_x86_64\bin\command.bat" -Dlogback.configurationFile=..\config\command_logback.xml -DDBX_COMMAND_LOG_LEVEL=INFO -cp ..\jars\command.jar com.splunk.dbx.command.DbxQueryCommand
12-12-2018 20:42:25.684 ERROR ChunkedExternProcessor - stderr: The system cannot find the file specified.
12-12-2018 20:42:26.203 ERROR ChunkedExternProcessor - stderr: 20:42:26.199 15800@W1835906 [main] INFO c.splunk.dbx.utils.TrustManagerUtil - action=load_key_manager_succeed
12-12-2018 20:42:26.295 INFO ChunkedExternProcessor - Custom search command is a generating command.
12-12-2018 20:42:26.295 INFO SearchPipeline - ReportSearch=1 AllowBatchMode=0
12-12-2018 20:42:26.295 INFO SearchPhaseGenerator - Disabling timeliner since source is not an event index
12-12-2018 20:42:26.295 INFO SearchPhaseGenerator - Disabling timeliner since event search is empty
12-12-2018 20:42:26.295 INFO SearchPhaseGenerator - No need for RTWindowProcessor
12-12-2018 20:42:26.295 INFO SearchPhaseGenerator - Timeliner will not be executed
12-12-2018 20:42:26.295 INFO SearchPhaseGenerator - required fields list to add to different pipelines =
12-12-2018 20:42:26.295 INFO SearchPhaseGenerator - Search Phases created.
12-12-2018 20:42:26.311 INFO UserManager - Setting user context: splunk-system-user
12-12-2018 20:42:26.311 INFO UserManager - Done setting user context: thunder_wu -> splunk-system-user
12-12-2018 20:42:26.311 INFO UserManager - Unwound user context: splunk-system-user -> thunder_wu
12-12-2018 20:42:26.311 INFO UserManager - Setting user context: thunder_wu
12-12-2018 20:42:26.311 INFO UserManager - Done setting user context: thunder_wu -> thunder_wu
12-12-2018 20:42:26.311 INFO UserManager - Unwound user context: thunder_wu -> thunder_wu
12-12-2018 20:42:26.311 INFO DistributedSearchResultCollectionManager - Stream search:
12-12-2018 20:42:26.312 INFO UserManager - Setting user context: thunder_wu
12-12-2018 20:42:26.312 INFO UserManager - Setting user context: thunder_wu
12-12-2018 20:42:26.312 INFO UserManager - Done setting user context: NULL -> thunder_wu
12-12-2018 20:42:26.312 INFO UserManager - Done setting user context: NULL -> thunder_wu
12-12-2018 20:42:26.312 INFO SearchPhaseGenerator - Result collation will occur at proc=dbxquery
12-12-2018 20:42:26.312 INFO UserManager - Setting user context: thunder_wu
12-12-2018 20:42:26.312 INFO UserManager - Done setting user context: NULL -> thunder_wu
12-12-2018 20:42:26.312 INFO UserManager - Setting user context: thunder_wu
12-12-2018 20:42:26.312 INFO UserManager - Setting user context: thunder_wu
12-12-2018 20:42:26.312 INFO UserManager - Done setting user context: NULL -> thunder_wu
12-12-2018 20:42:26.312 INFO UserManager - Done setting user context: NULL -> thunder_wu
12-12-2018 20:42:26.312 INFO SearchParser - PARSING: | streamnoop
12-12-2018 20:42:26.312 INFO SearchParser - PARSING: streamnoop | dbxquery connection=Realtime query="select 1 from DUAL;"
12-12-2018 20:42:26.313 INFO ChunkedExternProcessor - Running process: "C:\Program Files\Splunk\etc\apps\splunk_app_db_connect\windows_x86_64\bin\command.bat" -Dlogback.configurationFile=..\config\command_logback.xml -DDBX_COMMAND_LOG_LEVEL=INFO -cp ..\jars\command.jar com.splunk.dbx.command.DbxQueryCommand
12-12-2018 20:42:26.333 ERROR ChunkedExternProcessor - stderr: The system cannot find the file specified.
12-12-2018 20:42:26.336 ERROR ChunkedExternProcessor - stderr: 20:42:26.302 15800@W1835906 [main] WARN com.splunk.dbx.message.MessageEnum - action=initialize_resource_bundle_files error=Can't find bundle for base name Messages, locale en_US
12-12-2018 20:42:27.032 INFO ChunkedExternProcessor - Custom search command is a generating command.
12-12-2018 20:42:27.032 INFO SearchOrchestrator - Starting the status control thread.
12-12-2018 20:42:27.032 INFO SearchOrchestrator - Starting phase=1
12-12-2018 20:42:27.032 INFO UserManager - Setting user context: thunder_wu
12-12-2018 20:42:27.032 INFO UserManager - Setting user context: thunder_wu
12-12-2018 20:42:27.032 INFO UserManager - Done setting user context: NULL -> thunder_wu
12-12-2018 20:42:27.032 INFO UserManager - Done setting user context: NULL -> thunder_wu
12-12-2018 20:42:27.032 INFO ReducePhaseExecutor - Stating phase_1
12-12-2018 20:42:27.032 INFO SearchStatusEnforcer - Enforcing disk quota = 10485760000
12-12-2018 20:42:27.032 INFO DispatchExecutor - BEGIN OPEN: Processor=dbxquery
12-12-2018 20:42:27.032 INFO DispatchExecutor - END OPEN: Processor=dbxquery
12-12-2018 20:42:27.033 INFO PreviewExecutor - Preview Enforcing initialization done
12-12-2018 20:42:27.331 INFO ReducePhaseExecutor - ReducePhaseExecutor=1 action=PREVIEW
12-12-2018 20:42:27.352 ERROR ChunkedExternProcessor - stderr: 20:42:26.930 11508@W1835906 [main] INFO c.splunk.dbx.utils.TrustManagerUtil - action=load_key_manager_succeed
12-12-2018 20:42:27.352 ERROR ChunkedExternProcessor - stderr: 20:42:27.041 11508@W1835906 [main] WARN com.splunk.dbx.message.MessageEnum - action=initialize_resource_bundle_files error=Can't find bundle for base name Messages, locale en_US
12-12-2018 20:42:27.355 ERROR ChunkedExternProcessor - stderr: 20:42:27.046 15800@W1835906 [main] INFO c.s.d.s.driver.DriverServiceImpl - action=load_drivers multiple version drivers exist, 2 drivers found.
12-12-2018 20:42:27.355 ERROR ChunkedExternProcessor - stderr: 20:42:27.046 15800@W1835906 [main] INFO c.s.d.s.driver.DriverServiceImpl - driver name is com.splunk.dbx.service.driver.DelegatingDriver, select version 12.2, loaded from file ojdbc8.jar
12-12-2018 20:42:27.355 ERROR ChunkedExternProcessor - stderr: 20:42:27.048 15800@W1835906 [main] INFO c.s.d.s.driver.DriverServiceImpl - action=register_driver driver=oracle.jdbc.OracleDriver 12.2 succeeded
12-12-2018 20:42:27.355 ERROR ChunkedExternProcessor - stderr: 20:42:27.048 15800@W1835906 [main] INFO c.s.d.s.driver.DriverServiceImpl - action=load_drivers spent 101 ms to rescan all jdbc drivers
12-12-2018 20:42:27.355 ERROR ChunkedExternProcessor - stderr: 20:42:27.121 15800@W1835906 [main] INFO c.s.dbx.connector.ConnectorFactory - action=collect_connection_pool_metrics interval_in_seconds=60
12-12-2018 20:42:27.871 ERROR ChunkedExternProcessor - stderr: 20:42:27.750 11508@W1835906 [main] INFO c.s.d.s.driver.DriverServiceImpl - action=load_drivers multiple version drivers exist, 2 drivers found.
12-12-2018 20:42:27.871 ERROR ChunkedExternProcessor - stderr: 20:42:27.750 11508@W1835906 [main] INFO c.s.d.s.driver.DriverServiceImpl - driver name is com.splunk.dbx.service.driver.DelegatingDriver, select version 12.2, loaded from file ojdbc8.jar
12-12-2018 20:42:27.871 ERROR ChunkedExternProcessor - stderr: 20:42:27.752 11508@W1835906 [main] INFO c.s.d.s.driver.DriverServiceImpl - action=register_driver driver=oracle.jdbc.OracleDriver 12.2 succeeded
12-12-2018 20:42:27.871 ERROR ChunkedExternProcessor - stderr: 20:42:27.752 11508@W1835906 [main] INFO c.s.d.s.driver.DriverServiceImpl - action=load_drivers spent 102 ms to rescan all jdbc drivers
12-12-2018 20:42:27.871 ERROR ChunkedExternProcessor - stderr: 20:42:27.823 11508@W1835906 [main] INFO c.s.dbx.connector.ConnectorFactory - action=collect_connection_pool_metrics interval_in_seconds=60
12-12-2018 20:42:28.296 INFO PreviewExecutor - Stopping preview triggers since search almost finished
12-12-2018 20:42:28.317 INFO ReducePhaseExecutor - Ending phase_1
... View more