Informix Error -520: Cannot open database tblspace.

Reasons / Common Causes

-520 is a storage-layer failure: the server can't locate the disk partition (chunk) backing a table's tblspace, a server/administration-level problem rather than something wrong with the SQL statement itself.

1. The chunk backing the table's dbspace has been taken off-line, per the official guidance — the specific possibility it names directly.
2. A chunk file/device was removed, renamed, or became inaccessible at the OS level after the server had it open (a disk failure, an unmounted filesystem, a permissions change).
3. The instance was started with a chunk unavailable, so the affected dbspace never came fully on-line even though the instance itself is running.

Solutions / Resolution

1. Contact the database server administrator, per the official guidance — this is infrastructure-level, not something to work around from the application/SQL side.
2. Check whether the chunk is off-line, per the official guidance, as the administrator's first diagnostic step:

   onstat -d
   

   looking for the chunk's status flags (an off-line or down chunk is flagged in the output).
3. Bring the chunk back on-line, once the underlying storage issue (missing device, unmounted filesystem, permissions) is resolved, with onspaces -s:

   onspaces -s dbspace_name -p /path/to/chunk -o offset -O
   

   this only applies to a mirrored pair or a non-primary chunk in a noncritical dbspace; a non-mirrored primary chunk that's genuinely down typically requires a restore or IBM Informix Technical Support involvement instead.

Examples

Diagnosing from the administrator side

$ onstat -d
-- review chunk status flags for the dbspace backing the affected table

Diagnostic Checks

1. Run onstat -d to check whether the chunk backing the affected table's dbspace is reporting off-line or otherwise unavailable.
2. Check the OS level for the underlying storage problem (missing device file, unmounted filesystem, changed permissions) once a specific chunk is identified as the cause.

Related Errors / Related Topics

No closely related error codes are cross-referenced for -520 in this set yet.

An administration-level storage problem, not an application fix — escalate to whoever manages the instance and check chunk status with onstat -d.