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AdministeringIn addition to administering the database server, you can tune performance, replicate data, and archive data.
System administrationThese topics contain concepts, procedures, and reference information for database and database server administrators to use for managing and tuning HCL OneDB™ database servers.
Administrator's GuideThe HCL OneDB™ Administrator's Guide provides the information required to administer HCL OneDB™.
Disk, memory, and process management
Shared memoryThese topics describe the content of database server shared memory, the factors that determine the sizes of shared-memory areas, and how data moves into and out of shared memory.
Flush data to diskWriting a buffer to disk is called buffer flushing.
Types of writes during flushingTo provide you with information about the specific condition that prompted buffer-flushing activity, the database server defines three types of writes and counts how often each write occurs.
Foreground writeWhenever an sqlexec thread writes a buffer to disk, it is termed a foreground write. A foreground write occurs when an sqlexec thread searches through the LRU queues on behalf of a user but cannot locate an empty or unmodified buffer.

Foreground write

Whenever an sqlexec thread writes a buffer to disk, it is termed a foreground write. A foreground write occurs when an sqlexec thread searches through the LRU queues on behalf of a user but cannot locate an empty or unmodified buffer.

To make space, the sqlexec thread flushes pages, one at a time, to hold the data to be read from disk. For more information, see FIFO/LRU queues.

If the sqlexec thread must perform buffer flushing just to acquire a shared-memory buffer, performance can suffer. Foreground writes must be avoided. To display a count of the number of foreground writes, run onstat -F. If you find that foreground writes are occurring on a regular basis, tune the value of the page-cleaning parameters. Either increase the number of page cleaners or decrease the BUFFERPOOL lru_max_dirty value.