Threads shown by the onstat -g ath command
The threads that Enterprise Replication uses are shown by the onstat -g ath command.
The following table summarizes the threads that Enterprise Replication uses. You can use this information about threads when you evaluate memory use.
| Number of Threads | Thread Name | Thread Description |
|---|---|---|
| 1 | ddr_snoopy | Performs physical I/O from logical log, verifies potential replication, and sends applicable log-record entries to Enterprise Replication. |
| 1 | preDDR | Runs during queue recovery to monitor the log and blocks user transactions if the log position advances too far before replication resumes. |
| 1 | CDRGfan | Receives log entries and passes entries to evaluator thread |
| n | CDRGevaln | Evaluates log entry to determine whether to replicated it. The value of n is the number of evaluator threads specified by the CDR_EVALTHREADS configuration parameter. This thread also compresses committed transactions and queues completed replication messages. |
| 1 per large transaction | CDRPager | Performs the physical I/O for the temporary smart large object that holds paged transaction records. Grouper paging is activated for a transaction when its size is 10 percent of the value of the SHMVIRTSIZE or CDR_QUEUEMEM configuration parameters or when it includes more than 100,000 records. |
| 1 | CDRCparse | Parses all SQL statements for replicate definitions. |
| 1 per connection | CDRNsTnCDRNsAn | Sending thread for site. |
| 1 per connection | CDRNrn | Receiving thread for site. |
| 2...n | CDRACK_n | Accepts acknowledgments from site. At least 2, up to a maximum of the number of active connections. |
| # CPUs... | CDRD_n | Replays transaction on the target system (data sync thread). At least one thread is created for each CPU virtual processor (VP). The maximum number of threads is 4*(number of CPU VPs). |
| 1 | CDRSchedMgr | Schedules internal Enterprise Replication events. |
| 0 or 1 | CDRM_Monitor | Monitors and adjusts data sync performance for optimum performance (on the target). |
| 0 or 1 | CDRDTCleaner | Deletes rows from the deleted rows shadow table when they are no longer needed. |