Informix Error -191

Reasons / Common Causes

-191 is the chunk-level counterpart to -130 (dbspace) and -162 (blobspace): the chunk specified to be dropped doesn't exist under the identifier given.

1. A DROP CHUNK (or onspaces -d) command specifying a chunk that doesn't actually exist — a typo in the path, offset, or name identifying the chunk.
2. The chunk was already dropped previously, and a script or runbook attempts to drop it again — a non-idempotent decommissioning process re-running against something that's already gone.
3. Confusion about which specific chunk corresponds to a given dbspace, especially for a dbspace with multiple chunks — specifying an identifier that isn't actually part of the target dbspace, or doesn't exist at all.
4. Environment or configuration drift — a chunk defined in one environment's runbook doesn't exist in another environment the same runbook is run against.

Solutions / Resolution

1. Verify the chunk actually exists, and confirm the exact path/offset/name identifier before attempting to drop it:

   onstat -d
   

2. If the chunk was already dropped, no further action is needed — update the script or runbook to check for existence first, rather than assuming a chunk is always present before attempting to remove it.
3. Correct any typo in the chunk identifier used in the failing command.
4. For multi-chunk dbspaces, confirm exactly which chunk is intended before issuing the drop — don't rely on assumption when a dbspace has several chunks to choose from.

Examples

Verifying before dropping

onstat -d
-- confirm the exact chunk identifier (path and offset) before
-- attempting to drop it

Idempotent script logic

-- Instead of assuming the chunk exists:
onspaces -d dbspace1 -p /dev/chunk1 -o 0

-- Check first:
if chunk_exists("dbspace1", "/dev/chunk1", 0):
    onspaces -d dbspace1 -p /dev/chunk1 -o 0
else:
    log("chunk already removed — nothing to do")

Diagnostic Checks

1. List existing chunks and confirm identifiers:

   onstat -d
   

2. Review the exact command and identifier used in the failing drop attempt for a typo or mismatch.

Related Errors / Related Topics

• -130 — "ISAM error: no such dbspace." The dbspace-level sibling in the same existence-mismatch family.
• -162 — "ISAM error: Storage space does not exist." The blobspace-level sibling in the same family.

Run onstat -d first to confirm the chunk's actual identifier before assuming anything else is wrong — this resolves the overwhelming majority of -191 reports directly.