Sybase 12.4.2 - Manual (Page 321)

CHAPTER 8 Transactions and Versioning
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Cannot perform DDL command now as a DDL command is already in progress.
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.
Concurrency rules for
index creation
commands 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.