Sybase 12.4.2 manual 301

CHAPTER 8 Transactions and Versioning

Cannot perform DDL command now as a DDL command is already in progress.

Concurrency rules for index creation commands

If a CREATE DBSPACE or DROP DBSPACE command is in progress, and a user explicitly issues a CHECKPOINT command, the checkpoint fails with the message:

Run time SQL Error

If a CHECKPOINT command is in progress, a user who issues a CREATE DBSPACE or DROP DBSPACE command gets the following message:

Cannot perform requested command as there is a CHECKPOINT command in progress.

A user who issues CREATE DBSPACE during a drop gets the message

Cannot perform requested command as there is a DROP DBSPACE command in progress.

A user who issues DROP DBSPACE during a create gets the message:

Cannot perform requested command as there is a CREATE DBSPACE command in progress.

See “Versioning of temporary tables” for special rules regarding temporary tables.

When one transaction issues a DDL command on a given table or index, any other transaction that began before the DDL transaction commits, and that tries to access that table, receives an error.

When this error occurs, any additional attempts to read or write to the table in the current transaction will fail.

If a transaction modifies the definition of a table that is part of a join index, it locks every table with any columns that are joined in that index. This result occurs whether or not the particular columns in the original write transaction are being joined.

There is an exception to these rules for index creation commands. CREATE INDEX and CREATE JOIN INDEX can occur concurrently with a SELECT on the table(s) affected by the index creation. Adaptive Server IQ prevents use of the new index or join index until the transaction creating the index commits.

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