Concurrent Access to Tables with Exclusive Locks

After the LOCK TABLE statement with the IN EXCLUSIVE MODE option executes successfully, no other user can obtain a lock on the specified table. When you attempt a DDL operation on that table, however, you might receive RSAM error -106 if the same table is being accessed by a concurrent session (for example, by opening a cursor). This error can also affect implicit locks that certain DDL statements place on tables automatically.

This is possible because table locks do not preclude table access. An exclusive lock prevents other users from obtaining a lock, but it cannot prevent them from opening the table for write operations that wait for the exclusive lock to be released, or for Dirty Read operations on the table. You can set the IFX_DIRTY_WAIT environment variable to specify that the DDL operation wait for a specified number of seconds for Dirty Read operations to commit or rollback.