How Timestamps Help Keep Data Consistent

· Creation Timestamp (CTS)

· Update Timestamp (UTS)

CDS assigns a CTS to everything that is in a cell namespace: clearinghouses, directories, object entries, soft links, and child pointers. The CTS is a unique value reflecting the date, time, and location where a clearinghouse, directory, or entry in a directory was created. It consists of two parts: a time portion and the system identifier of the node on which the name was created. The two parts guarantee uniqueness among timestamps that are generated on different nodes.

During propagation of a new name or a changed name to each replica of the directory where it was created, every CDS server checks the validity of the CTS before accepting the new name.

The UTS reflects the most recent change that was made to any of the attributes of a clearinghouse, directory, object entry, soft link, or child pointer. When a CDS server receives an update to an existing entry in a directory, it checks the validity of the UTS before accepting the update.

Directories and replicas have several other timestamps that CDS uses when determining whether to skulk a directory or make a change in a directory. (See the directory(8dce) reference page for information about other timestamp attributes used by CDS.)