Memory-Related Parameters

The following are parameters related to the memory used by the Database Server or client. The type and value range for each parameter are as follows:

data_buffer_size

data_buffer_size is a parameter that configures the number of data pages to be cached in the memory by the Database Server. You can set units as K, M, G and T, which stand for KB (kilobytes), MB (megabytes), GB (gigabytes) and TB (terabytes), respectively. If you omit the unit, bytes will be applied. The default value is 512M, and the minimum value is 64K.

The greater the value of the data_buffer_size parameter, the more data pages to be cached in the buffer, thus providing the advantage of decreased disk I/O cost. However, if this parameter is too large, the buffer pool can be swapped out by the operating system because the system memory is excessively occupied. It is recommended to configure the data_buffer_size parameter in a way the required memory size is less than two-thirds of the system memory size.

• Required memory size = the number of buffer size (data_buffer_size)

index_scan_oid_buffer_size

index_scan_oid_buffer_size is a parameter that configures the number of buffer pages where the OID list is to be temporarily saved during the index scan.  You can set units as K, M, G and T, which stand for KB (kilobytes), MB (megabytes), GB (gigabytes) and TB (terabytes), respectively. If you omit the unit, bytes will be applied. The default value is 2M, and the minimum value is 64K.

The size of the OID buffer tends to vary in proportion to the value of the index_scan_oid_buffer_size parameter and the page size set when the database was created. In addition, the bigger the size of such OID buffer, the more the index scan cost. You can set the value of the index_scan_oid_buffer_size by considering these factors.

sort_buffer_size

sort_buffer_size is a parameter that configures the number of buffer pages to be used when sorting. You can set units as K, M, G and T, which stand for KB (kilobytes), MB (megabytes), GB (gigabytes) and TB (terabytes), respectively. If you omit the unit, bytes will be applied. The default value is 2M, and the minimum value is 64K.

The server assigns one sort buffer for each client request, and releases the assigned buffer memory when sorting is complete.

temp_file_memory_size_in_pages

temp_file_memory_size_in_pages is a parameter that configures the number of buffer pages to cache temporary result of a query. The default value is 4 and the maximum value is 20.

• Required memory size = the number of temporary memory buffer pages (temp_file_memory_size_in_pages * page size)
• The number of temporary memory buffer pages = the value of the temp_file_memory_size_in_pages parameter
• Page size = the value of the page size specified by the -s option of the cubrid createdb utility during the database creation

thread_stacksize

thread_stacksize is a parameter that configures the stack size of a thread. The default value is 100*1024. The value of the thread_stacksize parameter must not exceed the stack size allowed by the operating system.

garbage_collection

garbage_collection is a parameter that specifies whether or not to collect garbage memory no longer used by the client. The default value is no.