The customer was asking the meaning of this error:
These error details are shown in development mode.
To switch it off, change the operatingMode in jahia.properties.
Error: Pool size must be set and > 0
java.lang.IllegalArgumentException: Pool size must be set and > 0
The development environment was installed on one core machine and this environment does not fit the minimal configuration as defined in our documentation :
https://www.jahia.com/files/live/sites/jahiacom/files/resources/docs/7.x/7.0/en/DF7.0_Configuration-and-fine-tuning.pdf
Prerequisites (Minimal system requirements)