Poster: OCILobWrite on "OWNER"."TABLE_NAME" (4222468)

Shareplex supports replication of LOBs with some limitations. This solution provides a comprehensive list of such limitations

The following is a comprehensive list of limitations of LOBs. By LOBs, we mean all such data types like BLOB, CLOB, NCLOB etc. Here is the list:

• Shareplex does not support conflict resolution or transformation on table with LONG/LONG RAW or LOB columns as the value for these columns cannot be passed into the procedure.

• The tables with LOB data type cannot be contained in a config file which is activated with “live” option.

• SharePlex for Oracle command supports tables with LOB columns when the SP_DEQ_SKIP_LOB parameter is set to 0 when employing the compare config command. For more information about the SP_DEQ_SKIP_LOB parameter, see Shareplex Reference Guide Chapter titled “SharePlex Parameters”

• The “quickcheck” option of compare does NOT support LONG or LOB columns.
• Use one or more named export queues for tables containing LOBs. This automatically creates separate Export processes and named post queues with their own Post processes. Separating the processing of LOB data types should improve the overall speed of replication.

• If tables containing LOBs have referential integrity among one another, replicate them all using the same named queue.

• Replication of large LOBs has an effect on the SharePlex post queue. A SharePlex post queue actually consists of multiple subqueue files, each with a size of 8 MB. Subqueue files are added dynamically as needed. LOB activity can cause an unusually high number of subqueue files, which require additional shared memory. To ensure that SharePlex has enough shared memory when replicating LOBs, increase the SP_QUE_POST_SHMSIZE parameter to an initial setting of 60 MB. If SharePlex generates shared memory segment errors such as "rror: sp_cop process sp_mport/sp_opst_mt killed due to SIGSEGV" increase the setting. For instructions on setting SP_QUE_POST_SHMSIZE, see Shareplex Reference Guide Chapter titled “SharePlex Parameters”

• A table with LOBs cannot be configured for horizontally-partitioned replication.

• Peer-to-peer replication does not support replication of LOBs. If you enable LOB replication, they will be bypassed by conflict resolution, causing the potential for data to be out of synchronization.

• If the database is using the cost-based optimizer (CBO) and there are large numbers of LOBs in the tables that you are replicating, incorporate the SHAREPLEX_LOBMAP table, then put it into the analysis schedule. This table is updated frequently and must be analyzed frequently so that its indices remain efficient.

• SharePlex replicates the ALTER TABLE command to add a column except for adding a LOB column. To add a LOB column to a replicating table, use the procedure listed in Admin Guide Chapter titled “Changing Oracle Characteristics Of Replicated Objects”

• Enabling row movement on tables that contain LOBs is not supported.

• When replicating tables with LOBs, it is recommended to use one or more named export queues for tables containing LOBs. Thisautomatically creates separate export processes and named post queues with their own post processes.

• It is also recommended to separate the processing of LOB datatypes to improve the overall speed of replication.