This section reviews the causes and solutions for common synchronization problems. If you try these solutions and are still having problems, contact Quest Support.

For more information, see Understand the Concept of Synchronization.

If the issue you are experiencing is not listed in this documentation, search the SharePlex Knowledge Base at:

https://support.quest.com.

The Knowledge Base provides filtering options and links to other resources that can help you use and troubleshoot SharePlex.

How SharePlex reports out-of-sync conditions

For all objects except those involved in transformation, SharePlex verifies that the source and target data in a given operation are synchronized before posting the replicated data to the target. SharePlex does not verify synchronization if transformation is being used because:

• Transformation changes the target data, so before and after images cannot be compared.
• The transformation routine posts the data, not SharePlex.

When SharePlex determines that source and target data are different, it generates error conditions but continues to post other data from the post queue. To direct Post to stop processing altogether when it detects an out-of-sync condition, change the SP_OPO_OUT_OF_SYNC_SUSPEND (Oracle) or SP_OPX_OUT_OF_SYNC_SUSPEND (Open Target) parameter. See the Post parameter documentation in the SharePlex Reference Guide.

When an out-of-sync condition occurs, the Post process logs a message in the Status Database and also to the Event Log. To view these files in sp_ctrl:

• Status Database: Use the show statusdb or show sync command.
• Event Log: Use the show log command.

Use these commands frequently to monitor for out-of-sync errors.

The following is an example of how SharePlex reports an out-of-sync condition.

When data goes out of synchronization, SharePlex logs the failed SQL statements to the database_ID_errlog.sql file in the data sub-directory of the SharePlex variable-data directory.

Important: If you see an out-of-sync message in the Status Database and in the Event Log, but there is no record in the database_ID_errlog.sql file for the transaction, do not ignore those messages. They could be associated with a ROLLBACK. Regardless of whether or not a transaction is rolled back, SharePlex still compares the pre-images of the source and target rows. If they are different, that indicates that the data is out of synchronization. Only when a transaction is committed on the source but fails on the target does SharePlex log it to the database_ID_errlog.sql file, to give you a record of the statement that should have been applied as a tool for problem solving and for manually applying the statement if appropriate. Rolled back statements are canceled operations, and therefore not logged on the target.

Detect false out-of-sync conditions

Sometimes an out-of-sync message can be false, and the data is not out-of-sync. You can compare the source and target data by using the compare command, or you can perform the following comparison manually.

To compare with the compare command:

See the compare commands in the SharePlex Reference Guide.

To verify that data is out-of-sync:

1. Get the rowid of the affected row from the database_ID_errlog.sql file in the variable-data directory on the target system.
2. Using the rowid in the WHERE clause, run a SELECT query on the source table to get the row data for this rowid.
3. Run a SELECT query on the target table, using the row data that you got from the source query in the WHERE clause.
4. Compare the query results. If they are different, the rows are out of synchronization. If they are the same, the rows are synchronized.

Note: If none of the columns are unique in a table, Compare might show incorrect results.

Common out-of-sync conditions and solutions

The following are common ways in which data goes out of synchronization. In most cases, SharePlex detects out-of-sync conditions and returns an error message, but there are some situations where an out-of-sync condition is hidden, and SharePlex will not return an error.

Out of sync condition	Description	Solution
Incorrect cleanup procedure	If one of the database_cleansp cleanup utilities was run on some, but not all, systems associated with an active configuration, SharePlex perceives an out-of-sync condition.	Determine whether or not the cleanup utility was run on all systems by viewing the Event Log. The log tells you if and when it was run on each system. It also tells you if and when the configuration was activated. You can compare the times for those events to determine what happened. If the cleanup was not completed on all replication systems for this configuration, run the cleanup utility on all systems. Because the cleanup removes replication queues and processes and deactivates the configuration, you must perform initial synchronization again.
DDL changes	Some DDL-related causes of out-of-sync conditions are: Non-replicated DDL changes are made to source objects, but the configuration was not reactivated so that the objects can be re-analyzed. DDL that SharePlex replicates also gets performed manually on the target.	For a list of supported DDL, refer to the SharePlex Release Notes. To undo duplicate DDL changes made manually and also by SharePlex: Stop the Post process (it might already be stopped). sp_ctrl(sysB)> stop post Alter the target table to undo the DDL changes. Start Post and let SharePlex post the replicated DDL (which is still in the post queue). sp_ctrl(sysB)> start post
DML changes made directly to the target	If applications or users make DML changes to the tables on the target, the results of those changes will cause hidden out-of-sync conditions until Post attempts to apply a replicated change to the affected rows. When the change is applied, SharePlex returns an out-of-sync error.	Prevent all DML access to the target tables that are in replication. You can use the compare and repair commands to compare tables for out-of-sync rows and then repair those rows. For more information, see the command documentation in the SharePlex Reference Guide.
Triggers on target objects	Triggers must be disabled on target objects. The triggers fire on the source system and SharePlex replicates their effects to the target.	If triggers have fired on the target system, the objects changed by the triggers are out of synchronization and must be resynchronized. For more information, see How to Resynchronize Source and Target Tables. To disable the effects of triggers on target Oracle objects after the data is resynchronized, you can either of the following: Run the sp_add_trigger.sql script, which directs triggers to ignore the SharePlex Oracle user. See the utilities documentation in the SharePlex Reference Guide for more information about the trigger scripts. Disable the triggers if they are not needed.
Unnecessary constraints	The only constraints that are necessary on target tables in a one-way replication configuration are primary and unique key constraints. CHECK constraints are not necessary on the target because they are satisfied on the source. FOREIGN KEY and ON DELETE CASCADE constraints are also satisfied on the source, and SharePlex replicates the child operations to the correct tables on the target. For an Oracle target, you can leave ON DELETE CASCADE constraints enabled if you configure SharePlex to ignore them.	See Set up Oracle database objects for replicationSet up Oracle database objects for replication
Duplicate entries in the configuration file.	Duplicate entries, where the source, target, and routing map are identical, cause double posting on the target.	Copy the configuration file to a new file. Find and remove any duplicates in the new file. Perform a resynchronization and reactivation. For more information, see How to Resynchronize Source and Target Tables.
Lack of disk space	Data goes out of synchronization if user transactions continue when SharePlex does not have enough room to accommodate them in the queues. This can happen if: The network or target system was unavailable and too much data accumulated in the export queue. The target was unavailable and too much data accumulated in the Post queue. Capture lost pace with the logging of source transactions. In this case, data accumulates in the capture queue. A SharePlex process was stopped, but not restarted. The flush command was issued, but Post was not started again.	For more information, see How to Resolve Disk Space Shortage.
Changes to column conditions in horizontally partitioned replication	Out-of-sync conditions can result from the use of horizontally partitioned replication in the following cases: A column condition value is updated and the new value no longer satisfies the row selection criteria. A row that does not satisfy the column condition is updated to satisfy the condition.	Create column conditions so that partition shift does not occur. For more information, see Configure Horizontally Partitioned Replication.
Not reactivating after a configuration change.	If a table was added to the configuration, but the configuration was not reactivated, operations on that table are not being replicated. Note: For Oracle source tables, the auto-add feature is enabled by default, and any new table whose name satisfies a wildcard in the configuration file gets automatically added to replication. For more information, see Control Oracle DDL Replication.	Resynchronize the affected tables, then reactivate the configuration so that SharePlex can update its object cache. For more information, see How to Resynchronize Source and Target Tables.
Queue corruption	If the SharePlex queues are corrupted, such as if there is a system failure, the data in them can be lost. This requires a resynchronization.	For more information, see How to Resynchronize Source and Target Tables. (Oracle) To avoid queue corruption during system failure, you can use the parameter SP_QUE_SYNC. See the Queue parameters documentation in the SharePlex Reference Guide.

Oracle-related out-of-sync conditions and solutions

The following are common synchronization issues that relate specifically to replication between Oracle databases. In most cases, SharePlex detects out-of-sync conditions and returns an error message, but there are some situations where an out-of-sync condition is hidden, and SharePlex will not return an error.

Out of sync condition	Description	Solution
DDL changes	Some DDL-related causes of out-of-sync conditions are: Non-replicated DDL changes are made to source objects, but the configuration was not reactivated so that the objects can be re-analyzed. DDL that SharePlex replicates also gets performed manually on the target.	For a list of supported DDL, refer to the SharePlex Release Notes. To undo duplicate DDL changes made manually and also by SharePlex: Stop the Post process (it might already be stopped). sp_ctrl(sysB)> stop post Alter the target table to undo the DDL changes. Start Post and let SharePlex post the replicated DDL (which is still in the post queue). sp_ctrl(sysB)> start post
Inadequate or non-existing conflict resolution routines	Conflict resolution procedures are required in a peer to peer (active-active) configuration. SharePlex uses the conflict resolution procedures to determine which operation to post when the same data change is received from different systems.	Revise and test the conflict resolution procedures, then resynchronize the data. For more information, see How to Resynchronize Source and Target Tables.
Log wrap	If the redo logs wrap before Capture can process the data it needs, the data can go out of synchronization if archived logging is not enabled or if the archive logs needed by Capture were removed. (Normally, Capture would access the archive logs and continue replicating.)	See Correct the problem first If archiving is not enabled, there are no archive logs for SharePlex to read. Data lost after the log wrap cannot be recovered. Enable archived logging, and resynchronize the data. For more information, see How to Resynchronize Source and Target Tables. If SharePlex is many logs behind Oracle, consider resynchronizing the data instead of restoring the logs. It might take less time than Capture would take to process the missing records from the archive logs. In addition, it eliminates the possibility that the capture queue could exceed free disk space while processing the archive logs. You can base your decision on the size of the redo logs and the number of tables being replicated, both of which determine how much information Capture must process. Also take into consideration how much latency the users of the target data can tolerate. If archive logs are available, copy the appropriate logs back to the archived-log directory on the source system, or use the SP_OCT_ARCH_LOC parameter to point SharePlex to their location.
LONG columns	If a table has no primary or unique key, SharePlex builds a simulated key based on all of the columns except the LONG and LOB columns. If the LONG columns in the target rows are the only columns that contain unique values, multiple rows could meet the criteria for the simulated key. SharePlex could apply the UPDATE or DELETE to the wrong row without the error being detected, causing the table to go out of synchronization without an error message.	If you can create a key from columns that ensure uniqueness on the target table(s), you can avoid this kind of out-of-sync condition. After you create the key, resynchronize and re-activate those objects so that SharePlex can update its object cache. If adding a primary or unique key is not possible (such as when packaged applications are in use), uniqueness of rows on the target system cannot be ensured.
Changes to keys	If tables use automatically generated numerical sequences as keys, and a key value changes, this may cause duplicity on the target system. If the new value already exists as a key in another row on the target system, SharePlex returns a unique-key constraint violation and out-of-sync error. This can happen when you update values using an x +n formula, where n is an incremental increase. It is possible that one of the x +n values will equal an existing value.	Create the sequences so that the updates cannot result in a duplication of keys on the target system.
DBMS_SCHEDULER procedures running on source and/or target system	The effects of these procedures, such as objects being created, manipulated and dropped outside replication, may not be visible to replication or may not be supported, resulting in data changes that cause out-of-sync conditions.	Exclude source and target objects from the jobs.
Virtual private database	If replicating data that is configured as a virtual private database, the SharePlex database user may not have the access rights to capture the data. Any changes to that data will not be reflected on the target.	If you do not need that data replicated to the target, you can filter it out of the SharePlex configuration by means of partitioned replication. If you want the data to be replicated, assign the SharePlex user the correct access rights.
PK/UK logging not enabled	Certain replication problems can be prevented by logging key values. SharePlex fetches key values based on the rowid. Any operation that changes the rowid, such as ALTER TABLE...MOVE, can cause the wrong key values to be used for subsequent DML operations.	SharePlex recommends that both primary key and unique key supplemental logging be set, or that a supplemental log group on unique columns be defined for every table in replication.

Correct the problem first

If data is out-of-synchronization, do the following before you resynchronize the data:

1. Determine why it happened before you resynchronize the data. Otherwise, the problem can repeat itself and result in more data going out of synchronization.
2. Stop the Post process to prevent further errors. If the accumulation of messages in the Post queue is threatening to cause disk space issues, and if there is enough disk space available on the source system, you can stop Import until Post can clear out some of the operations from other transactions. For more information, see How to Resolve Disk Space Shortage.
3. View the Status Database and the Event Log to determine the cause of the problem.
4. Resolve the problem.

Resynchronize data

For more information, see How to Resynchronize Source and Target Tables.