PLOAD_SHMBASE Environment Variable

The PLOAD_SHMBASE environment variable allows you to specify shared-memory address attachments specifically for onpload processes. You can set the PLOAD_SHMBASE environment variable to avoid shared-memory collisions between onpload and the database server or allow the HPL to specify the attachments.

Avoiding Shared-Memory Collision

Both the database server and onpload allocate shared memory. When onpload starts up, the database server allocates shared memory for buffers for onpload processes. The onpload utility also allocates shared memory for its internal use. Because of the dynamic nature of shared-memory allocations, shared-memory collisions can occur between onpload and the database server. If this occurs, the onpload job can also fail and error messages are sent to the onpload log file or the database server log file.

To verify if a collision has occurred, use the onstat -g seg option. Check for overlap between the shared-memory segments that the database server is using and the SHMBASE reported in the onpload log file.

For more information on the onstat -g seg option, see the IBM Informix: Dynamic Server Administrator's Guide and the IBM Informix: Dynamic Server Administrator's Reference.

Setting the PLOAD_SHMBASE Environment Variable

To override the initial shared-memory allocation in case of a shared-memory collision between onpload and the database server, set the PLOAD_SHMBASE environment variable to a value much higher or much lower than that for the shared memory that the database server uses.