http://docs.openlinksw.com/virtuoso/repl.html Data Replication, Synchronization and Transformation Services OpenLink Virtuoso Universal Server: Documentation virtuoso.docs@openlinksw.com virtuoso.docs@openlinksw.com 2008-07-28T11:35:38Z OpenLink Software Documentation Team http://docs.openlinksw.com/virtuoso/../images/misc/logo.jpg http://docs.openlinksw.com/virtuoso/replintro.html virtuoso.docs@openlinksw.com virtuoso.docs@openlinksw.com Introduction 2008-07-28T11:35:38Z Introduction Virtuoso provides several replication methods: http://docs.openlinksw.com/virtuoso/SNAPSHOT.html virtuoso.docs@openlinksw.com virtuoso.docs@openlinksw.com Snapshot Replication 2008-07-28T11:35:38Z Snapshot Replication http://docs.openlinksw.com/virtuoso/proctransrepl.html virtuoso.docs@openlinksw.com virtuoso.docs@openlinksw.com Transactional Replication 2008-07-28T11:35:38Z Transactional Replication The unit of replication is a publication. A publication is an ordered sequence of transaction entries. One database transaction can add data to zero or more publications. The data contributed to a publication by a transaction is appended to the publication at the time of commit. Because commits are serialized database wide, items in a publication have a well defined order. Each transaction entry in a publication has a unique sequence number within the publication. Each subscriber of a publication has a level of synchronization, which is the serial number of the last transaction from the publication which this subscriber has processed. Each publication has exactly one publisher and zero or more subscribers. Any multi-master merge replication schemes will be based on this notion, with data to be merged back into the original source regarded as a separate publication and the merge regarded as a process between publications. http://docs.openlinksw.com/virtuoso/SCHEDULER.html virtuoso.docs@openlinksw.com virtuoso.docs@openlinksw.com Virtuoso scheduler 2008-07-28T11:35:38Z Virtuoso scheduler Virtuoso scheduler allows an arbitrary SQL command to be run at certain intervals. The scheduler process wakes up every n minutes, scans the SYS_SCHEDULED_EVENT table and executes each command which applies to the current time. Note that overdue commands are executed only once. There is a virtuoso.ini parameter "Scheduler interval" under "Parameters" section which defines the scheduler wake-up interval. Set this to 0 (the default) to disable the scheduler. http://docs.openlinksw.com/virtuoso/replexamples.html virtuoso.docs@openlinksw.com virtuoso.docs@openlinksw.com Transactional Replication Example 2008-07-28T11:35:38Z Transactional Replication Example http://docs.openlinksw.com/virtuoso/replsample.html virtuoso.docs@openlinksw.com virtuoso.docs@openlinksw.com Replication Logger Sample 2008-07-28T11:35:38Z Replication Logger Sample The logger directory in the samples in the distribution contains a simple load balancing sample. It implements a simplified web site hit log where there is a count of hits maintained per user name and origin IP of each hit. Thus the transaction being replicated between the servers consists of incrementing an IP's hit count and then incrementing a user's hit count. If either IP or user do not have a count, a row is added with a count of 1. The transaction is then logged for replication, so that all servers get all hits, no matter which of the replicating servers processes the hit. The application client calls wl_hit on one of the mutually replicating servers to log an event. The event's trace will then be propagated to all other servers. The wl_hit_repl function does the actual work. The top level function calls this plus logs the call with its arguments on the local server's hits publication for distribution to other servers.