Data and Transaction Management

All tables in SAP Sybase IQ are stored in the IQ main store. This on-disk storage is table-level versioned (TLV). When a table is enabled for row-level versioning (RLV), the on-disk version remains fixed, and the in-memory RLV store is activated. As table transactions are performed, the server manages many row-level versions which are committed and stored in-memory. Over time, this data from the RLV store is merged with the IQ main store.

• Data Modification Language (DML)
  The disk I/O per row in the RLV store is substantially less than in the IQ main store, thus enabling smaller-granularity DML.
• Transaction Management
  The transaction manager includes support for transaction access to the RLV store. The transaction manager works the version manager to provide table- and row-level versioning support.
• Lock Management
  Row locks, and their prerequisite write-intent locks, ensure consistency between concurrent transactions at a row level. For example, a transaction can lock a particular row to prevent another transaction from changing it. Transactions place write-intent locks on the table itself, and on the table rows they intend to modify, to prevent conflicts from both competing row-level and table-level snapshot-versioned transactions.
• Version Management
  Transactions involving RLV-enabled tables create row-level transaction snapshot versions. A row-level snapshot allows the transaction to commit a version of the table row, rather than a version of the entire table.