DSE can operate concurrently with normal access by the GT.M run-time system. This lets you perform an investigation and some types of repairs with minimal disruption.

Some repairs should only be undertaken by a process that has standalone access to the database, while other repairs present no danger when performed with other users accessing the file. However, there is still some risk with the latter type of repairs, depending on the "placement" of the error and the likelihood of concurrent access to that area of the database.

Unless availability is a critical problem, Fidelity Information Services recommends performing all repairs in standalone mode to ensure the safety of data. For environments where availability is an issue, your knowledge of the application and how it is used are the best guides in assessing the risk of performing concurrent repairs. To help you assess the amount of risk, the following sections identify repairs that should only be undertaken with standalone access.

If you attempt concurrent repairs, plan the order of your updates carefully. Always REMOVE the index record that points to a block before using MAP -FREE on that block. Always MAP a block -BUSY and assure that it meets GDS design criteria and accomplishes the repair goal before using ADD to create an index record that points to that block.