In a well-tuned Enterprise Replication system, the send queue and receive queue should not regularly overflow from memory to disk. However, if the queues in memory fill, the transaction buffers are written (spooled) to disk. Spooled transactions consist of transaction records, replicate information, and row data. Spooled transaction records and replicate information are stored in the transaction tables and the replicate information tables in a single dbspace. Spooled row data is stored in one or more sbspaces.
For more information, see Setting Up Send and Receive Queue Spool Areas.
The following situations can cause Enterprise Replication to spool to disk:
If the receiving server or network connection is down or suspended, Enterprise Replication might spool transaction buffers to disk.
To check for a down server or network connection, run cdr list server on a root server. This command shows all servers and their connection status and state.
For more information, see Viewing Replication Server Attributes and cdr list server.
If a replicate is suspended, Enterprise Replication might spool transaction buffers to disk.
To check for a suspended replicate, run cdr list replicate. This command shows all replicates and their state.
For more information, see Viewing Replicate Properties and cdr list replicate.
Enterprise Replication is optimized to handle small transactions efficiently. Very large transactions or batch jobs force Enterprise Replication into an exceptional processing path that results in spooling. For best results, avoid replicating these types of transactions.
For more information, see Large Transactions.
If the logical log files are too small or the number of logical log files is too few, Enterprise Replication is more likely to spool transaction buffers to disk.
To increase the size of the logical logs, see the chapter on logical logs in the IBM Informix Dynamic Server Administrator's Guide. For more information on configuring your logical log files for use with Enterprise Replication, see Logical Log Configuration Guidelines.
If a server is low on resources, Enterprise Replication might not be able to hold all transactions replicating from a source server in memory during processing, and the transactions spool to disk.
If this happens, check the system resources; in particular, check disk speed, RAM, and CPU resources.