From version 2.8 onwards Replicate parameters APPLY_LOOP_PREVENTION and MINE_LOOP_PREVENTION will become public ones.
This page is trying to shed some light onto the meaning of the APPLY_LOOP_PREVENTION and MINE_LOOP_PREVENTION parameters.
Replicate does filtering of transactions based on TRANSACTION_NAME which contains "DBREPL_database_name_XID".
APPLY_LOOP_PREVENTION ( YES on default)
Purpose:
- Changes that are mined on the source server and then applied on the target server are not mined again on the target server. This is prevented by the APPLY_LOOP_PREVENTION setting.
- Based on TRANSACTION_NAME the APPLY_LOOP_PREVENTION throws transaction out on APPLY - if the database name matches current database meaning it just completed a loop.
- It also checks if the DDL was done by an apply process on this db; modify the DDL by adding comment to the end so next mine/apply can check that it was done by apply.
Valid Settings: YES or NO
MINE_LOOP_PREVENTION ( NO on default)
Purpose:
- Changes that are mined on the source server and then applied on the target server. This is controlled by the MINE_LOOP_PREVENTION setting.
- MINE_LOOP_PREVENTION throws out transaction based on the TRANSACTION_NAME that contains "DBREPL_database_name_XID".
If set to YES it checks if Replicate does skip this DDL due to:
- it is created by an APPLY process and APPLY adds a comment to end of the DDL.
This is disabled - Replicate need to pass at least CREATE TABLE to APPLY; it just lets APPLY_LOOP_PREVENTION do it's job for DDL
- an established isolation level triggered by a SET TRANSACTION statement
Comment: MINE_LOOP_PREVENTION is preferred to APPLY_LOOP_PREVENTION as the changes are filtered sooner and don't even get written to a PLOG file. But it's too aggressive in more complicated scenarios.
Valid Settings: YES or NO
If both APPLY_LOOP_PREVENTION and MINE_LOOP_PREVENTION are disabled APPLY will not set/use transaction name 'DBREPL_%'.
Bi-direction (or 2-way): replication is possible allowing master-to-master replication to provide real time information across multiple applications and sites.
One-way replication is possible allowing real time reporting across distributed reader farms reducing the performance impact on the production databases.