The collector queue IPAM.DHCP.Subnet.Polling.db keeps growing in IPAM

2/9/2026 11:31 AM

2/9/2026 4:40 PM

In SolarWinds IP Address Manager (IPAM), the file:

C:\ProgramData\SolarWinds\Collector\Queues\IPAM.DHCP.Subnet.Polling.db

is the local SQLite queue for IPAM DHCP subnet polling. When this queue file keeps growing (for example, back to ~1 GB shortly after deletion), it indicates that:

• IPAM DHCP subnet polls are being enqueued, but

• Something prevents those scan results from being processed and committed.

In the IPAM.DHCP.Subnet.Polling.log file, you may see repeated errors similar to:

2026-02-05 05:07:25,544 [STP DatabaseProcessing Thread #962] ERROR SolarWinds.IPAM.Collector.DHCPSubnet.DhcpSubnetPollingPlan - Scan idled away: IpRangeString was blank for subnet id = 4130
2026-02-05 05:22:44,838 [STP DatabaseProcessing Thread #1037] ERROR SolarWinds.IPAM.Collector.DHCPSubnet.DhcpSubnetPollingPlan - Scan idled away: IpRangeString was blank for subnet id = 4121
2026-02-05 05:41:50,551 [STP DatabaseProcessing Thread #1055] ERROR SolarWinds.IPAM.Collector.DHCPSubnet.DhcpSubnetPollingPlan - Scan idled away: IpRangeString was blank for subnet id = 5007
2026-02-05 05:43:15,269 [STP DatabaseProcessing Thread #1055] ERROR SolarWinds.IPAM.Collector.DHCPSubnet.DhcpSubnetPollingPlan - Scan idled away: IpRangeString was blank for subnet id = 4147
2026-02-05 05:55:43,095 [STP DatabaseProcessing Thread #1055] ERROR SolarWinds.IPAM.Collector.DHCPSubnet.DhcpSubnetPollingPlan - Scan idled away: IpRangeString was blank for subnet id = 4093
2026-02-05 06:10:13,762 [STP DatabaseProcessing Thread #1105] ERROR SolarWinds.IPAM.Collector.DHCPSubnet.DhcpSubnetPollingPlan - Scan idled away: IpRangeString was blank for subnet id = 4391

When this occurs, you typically find:

• A large number of stuck IPAM scan queues in the IPAM_ScanInstance table.

• Multiple invalid scopes in IPAM_Group (rows where FriendlyName ends with [INVALID]).

These invalid scopes prevent successful processing of DHCP subnet polling jobs, causing the queue file to continually refill.

IP Address Manager

The issue is caused by invalid or mismatched DHCP scopes in IPAM that result in stuck DHCP subnet polling jobs:

• The queue file IPAM.DHCP.Subnet.Polling.db is the local SQLite queue used by the IPAM DHCP subnet polling engine.

• If there are many invalid scopes and stuck scan instances:

  • IPAM keeps enqueuing DHCP subnet polls, but

  • The engine cannot complete processing because IpRangeString is blank for one or more subnets.

In IPAM_Group, scopes marked as [INVALID] in the FriendlyName column indicate that the DHCP scope definition on the DHCP server no longer matches the corresponding subnet in IPAM. Typical scenarios include:

• The mask/CIDR or IP range was changed on the DHCP server, but the IPAM subnet still uses the old definition.

• The scope was deleted or renamed on the DHCP server, but the corresponding subnet/scope still exists in IPAM (orphaned entry).

When IPAM detects this mismatch, it renames the scope display to include [INVALID] and treats it as invalid until you remove the invalid entry from IPAM and rescan the DHCP server so that the correct definition is rediscovered.

As long as these invalid scopes remain, the polling jobs for those subnets cannot complete successfully, and the queue file continues to grow.

Important: Before running any SQL script against the SolarWinds database, take a full backup of the SolarWinds Platform database.

1. Back up the SolarWinds database

1. Take a full backup of the SolarWinds Orion database using your usual SQL backup process.

2. Confirm that the backup completes successfully before proceeding.

2. Clear stuck IPAM scan queues in the database

Deleting the local .db file only clears the local collector queue. If the SQL tables still hold a large number of pending scan instances, the polling engine immediately re‑queues them and the file quickly grows again.

To inspect and, if necessary, clear the IPAM scan queue:

1. Connect to the SolarWinds Orion database using SQL Server Management Studio (SSMS) or Orion Database Manager.
   For guidance on running SQL queries, see the article How to Run a SQL Query in Orion Database Manager on Windows Server 2008.

2. Run the following queries to review the current IPAM scan queues:

 

-- Scripts are not supported under any SolarWinds support program or service.
-- Scripts are provided AS IS without warranty of any kind. SolarWinds further
-- disclaims all warranties including, without limitation, any implied warranties
-- of merchantability or of fitness for a particular purpose. The risk arising
-- out of the use or performance of the scripts and documentation stays with you.
-- In no event shall SolarWinds or anyone else involved in the creation,
-- production, or delivery of the scripts be liable for any damages whatsoever
-- (including, without limitation, damages for loss of business profits, business
-- interruption, loss of business information, or other pecuniary loss) arising
-- out of the use of or inability to use the scripts or documentation.

SELECT COUNT(*) AS TotalScanInstances FROM IPAM_ScanInstance;

SELECT TOP 50 *
FROM IPAM_ScanInstance
ORDER BY ScanDate DESC;

3. If the TotalScanInstances count is very high or clearly not draining over time, truncate the queue to flush the stuck IPAM DHCP subnet scan jobs:

-- Scripts are not supported under any SolarWinds support program or service.
-- Scripts are provided AS IS without warranty of any kind. SolarWinds further
-- disclaims all warranties including, without limitation, any implied warranties
-- of merchantability or of fitness for a particular purpose. The risk arising
-- out of the use or performance of the scripts and documentation stays with you.
-- In no event shall SolarWinds or anyone else involved in the creation,
-- production, or delivery of the scripts be liable for any damages whatsoever
-- (including, without limitation, damages for loss of business profits, business
-- interruption, loss of business information, or other pecuniary loss) arising
-- out of the use of or inability to use the scripts or documentation.

TRUNCATE TABLE IPAM_ScanInstance;

Impact: IPAM will need to re‑schedule subnet scans. Expect a catch‑up cycle while scans are re‑queued and processed, but the infinite queue growth should stop.

 

3. Remove invalid DHCP scopes from IPAM

Invalid scopes in IPAM_Group (where FriendlyName ends with [INVALID]) must be removed so that IPAM stops attempting to poll them.

1. Identify invalid scopes with the following query:

-- Scripts are not supported under any SolarWinds support program or service.
-- Scripts are provided AS IS without warranty of any kind. SolarWinds further
-- disclaims all warranties including, without limitation, any implied warranties
-- of merchantability or of fitness for a particular purpose. The risk arising
-- out of the use or performance of the scripts and documentation stays with you.
-- In no event shall SolarWinds or anyone else involved in the creation,
-- production, or delivery of the scripts be liable for any damages whatsoever
-- (including, without limitation, damages for loss of business profits, business
-- interruption, loss of business information, or other pecuniary loss) arising
-- out of the use of or inability to use the scripts or documentation.

SELECT TOP 1000 * FROM [dbo].[IPAM_Group]
WHERE FriendlyName LIKE '%INVALID%'

2. Decide how to remove these invalid scopes:

   • Preferred (UI-based):

     • Use the SolarWinds Platform Web Console to locate and remove the corresponding invalid scopes/subnets in IPAM.

     • After removal, rediscover or rescan the DHCP servers so that valid scopes are re-added with correct definitions.

   • Direct SQL delete:

-- Scripts are not supported under any SolarWinds support program or service.
-- Scripts are provided AS IS without warranty of any kind. SolarWinds further
-- disclaims all warranties including, without limitation, any implied warranties
-- of merchantability or of fitness for a particular purpose. The risk arising
-- out of the use or performance of the scripts and documentation stays with you.
-- In no event shall SolarWinds or anyone else involved in the creation,
-- production, or delivery of the scripts be liable for any damages whatsoever
-- (including, without limitation, damages for loss of business profits, business
-- interruption, loss of business information, or other pecuniary loss) arising
-- out of the use of or inability to use the scripts or documentation.

DELETE FROM [dbo].[IPAM_Group]
WHERE FriendlyName LIKE '%[INVALID]%'

4. Repair Job Engine v2 and Collector Services

To ensure that the IPAM DHCP subnet polling engine and related services are healthy:

1. Follow the steps in the article
   “Repair a failing Job Engine and Collector Components” to repair:

   • Job Engine v2

   • Collector Service

2. After the repair:

   • Confirm that the services start successfully.

   • Monitor:

     • The size of IPAM.DHCP.Subnet.Polling.db

     • The IPAM.DHCP.Subnet.Polling.log for repeated IpRangeString was blank errors.

     • The count of rows in IPAM_ScanInstance to ensure it is now draining as expected.