In order for a database to start, all files of IQ_SYSTEM_MAIN, all files of IQ_SYSTEM_TEMP, and the catalog file SYSTEM must be available. A database can be started skipping other user and catalog dbspaces that cannot be fully opened. All read-write files of IQ main store dbspaces other than the IQ_SYSTEM MAIN dbspace and any catalog dbspace other than SYSTEM that cannot successfully open all files of the dbspace, logs an error and marks the dbspace dynamically offline (marked offline in memory, as opposed to marking it offline in the catalog). If all files of IQ_SYSTEM_TEMP cannot be opened, the database will not start unless the -iqnotemp startup parameter is used.
Sybase IQ consistency checks the commit_id in each dbspace file header against the value in the system tables ISYSDBFILE and ISYSIQDBSPACE and marks any file or dbspace that does not match offline as above.
A dbspace that has been marked offline at start time may be brought online via the ALTER DBSPACE ONLINE statement, assuming that the problem has been corrected and the dbspace can be opened.
A table object that resides in an offline dbspace is unavailable. Any DDL or DML request except ALTER DBSPACE ONLINE to any table object in an offline dbspace generates an error. Note that after you make a dbspace offline, there may still be data pages in the buffer cache. In the case of a very small table, the entire table may be in memory in the buffer cache and temporarily available, even if the dbspace is offline.
