Handle potential log wrapping

The potential for log wrap occurs when Enterprise Replication log processing lags behind the current log and the Enterprise Replication replay position is in danger of being overrun.

There are two log positions you should be aware of: the snoopy log position, which is the log position that keeps track of transactions being captured for replication, and the log replay position, which is the log position that keeps track of which transactions have been applied.

A potential log wrap situation is usually caused by the logical logs being misconfigured for the current transaction activity or by the Enterprise Replication system having to spool more than usual. More-than-usual spooling could be caused by one of the following situations:
  • A one-time job might be larger than normal and thus require more log space.
  • One of the target servers is currently unavailable and more spooling of replicated transactions is required.
  • The spool file or paging space could be full and needs to be expanded.

You can configure how Enterprise Replication responds to a potential log wrap situation by specifying one or more of the following solutions, in order of priority, with the CDR_LOG_LAG_ACTION configuration parameter:

For example, you can specify that during a potential log wrap situation, Enterprise Replication stages compressed logical logs. If the log staging directory reaches its maximum size, then logical logs are added. If the maximum number of logical logs are added, then Enterprise Replication blocks user transactions. Not all options can be combined together in every possible priority order. For example, specifying to stop Enterprise Replication, to ignore the potential for log wrap, or to block user actions must always be either the only option or the last option in the list.


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