There are many KBases surrounding this error.
1352299 - Error:"An internal error occured while calling 'processDPCommands' API. (Error:ERR_WIS_30270) " while refreshing the Webi Report in Infoview
1568293 - "ProcessDPCommnands API Error" while refreshing WebI report in InfoView and Web Intelligence Rich Client.
1643514 - Error "An internal error occured while calling 'processDPCommands' API. (Error: ERR_WIS_30270)" when cancel the query in Web Intelligence document
A few thing to check\test would be:
Change CMC server properties:
Please go to Central Management console.
Go to Servers.
From left hand side panel select Server categories and then Web intelligence.
Right click the Webintelligenceprocessingserver and select Properties.
Set Binary Stream Maximum size to 500 (it is in MB).
Set Maximum character stream size to 500 (it is in MB).
Click save and close.
Change in webi.properties file:
Open the 'webi.properties' form this location and make the required changes to changes the Heap size.
D:\Program Files (x86)\Business Objects\Tomcat55\webapps\AnalyticalReporting\WEB-INF\classes
Add the following line to the end of the webi.properties file (assuming that the Java Heap Max is set to 1024):
Note: The default value of MAX_HEAP_SIZE is 5000000 and is appropriate for a Java Heap setting of 512.
Stop and then restart the Tomcat application server.
Note: The Tomcat limitation for the Heap Size setting is 1.5 GB (1536 MB), but the higher the value you set, the worse the performance when you run reports. If you try to increase the value higher than this, then Tomcat will not start.
I hope this is a very, very helpful answer to you.