The recommended procedure for maintaining synchronized data through the comparison and repair commands is to run the compare or compare using command first, then view the results with the repair status command. This command shows any rows that are out-of-sync and the possible cause. Unless the cause of the out-of-sync condition is corrected, replication will go out of synchronization again, even if you repair the rows this time. After the problem is fixed, issue the repair or repair using command.

You can run the repair or repair using command without doing a preliminary comparison. The command performs a comparison first, to identify the out-of-sync rows, and then it repairs those rows. However, the underlying cause of the out-of-sync condition must be corrected to prevent future out-of-sync conditions.

See for causes and solutions for out-of-sync conditions.

To view the status or results of a comparison, use the compare status command in sp_ctrl.

To view the status or results of a repair, use the repair status command in sp_ctrl.

When to run a repair

The best time to repair a target table depends on its size, the cause of the problem, the extent of out-of-sync rows, and how long you are willing to tolerate users being locked out. Before you initiate a repair, consider the following:

• Although the users of the tables are not usually affected by the brief locks that are applied when tables are compared, they are locked out of the target table for the duration of the repair process. For a small table, this might not be disruptive, but for a large table needing extensive repairs, the wait can be significant.
• Locks on a target table can reduce posting performance if Post must wait for the repair to finish before it can apply changes to that table and move on to other tables. This increases the latency of the target data and causes operations to accumulate in the post queue. If the objects that Post needs to change are different from those being repaired, the two processes run simultaneously.

• If you must repair a table immediately, but cannot tolerate locks or replication latency, you can use the where option to limit the repair to certain rows. An alternative is to use the key option, but this option may cause the repair to miss some out-of-sync rows.

• If the repair can wait, correct the cause of the problem immediately and then do the repair during non-peak hours.

• Replication latency can slow down the compare and repair processing. The message sent from the source to spawn the command processes on the target is sent through the queues along with regular replicated data. Delays caused by a data backlog will delay the spawn message and cause the process on the source to lose its read consistency, which results in errors. If possible, perform comparisons and repairs during off-peak hours.

How to run the compare and repair commands

To get additional information and syntax for the compare and repair commands, see the command documentation in theSharePlex Reference Guide.