Use the Executor command cache to cache column names and datatypes for a primary Adaptive Server database table, when a Sybase RepAgent initially sends an insert, delete, or update LTL command for that table.
Metadata such as column name and datatype are part of the table schema that RepAgent sends as well as the data associated with an
insert,
delete, or
update command. However, with caching:
- RepAgent sends the metadata and data associated with an insert, update, or delete command only when the RepAgent processes an operation for that specific table the first time since the RepAgent started, or since a connection with Replication Server was restarted. RepAgent does not send the table metadata when RepAgent subsequently processes transactions for that table.
- RepAgent can resend metadata and data if there is not enough memory in the RepAgent to keep all the schema definitions.
- RepAgent sends the metadata and data of a table when the RepAgent processes a modification on a specific table after the table schema has been changed, for example, after an Adaptive Server alter table operation.
To replicate subsequent operations on the same table, RepAgent sends only the column data, since the Replication Server Executor command cache stores the metadata. The combination of RepAgent metadata reduction and using the Replication Server Executor command cache improves replication performance because caching:
- Reduces the time spent by RepAgent packing metadata into the Log Transfer Language (LTL) packet.
- Reduces network traffic by increasing the amount of data sent in each packet.
- Allows RepAgent to dedicate the time saved to scanning the primary database log instead of packing metadata.
- Allows the Replication Server Executor to process tables with large number of columns more efficiently.
Note: The cache contains only metadata from tables that have been modified by an insert, update, or delete operation.
See Replication Server Administration Guide Volume 2 > Performance Tuning > Suggestions for Using Tuning Parameters > Executor Command Cache.
System Requirements
Table metadata reduction requires LTL version 740 or later, and Adaptive Server 15.7 or later.