# Error in Restore snapshot **URL:** \ **Category:** Community\ **Created:** [August 2, 2024, 6:23pm UTC](https://community.questdb.com/t/error-in-restore-snapshot/141 "2024-08-02T18:23:05Z")\ **Posts on this page:** 4\ **Page:** 1
**Author:** ![ilana8](https://avatars.discourse-cdn.com/v4/letter/i/848f3c/32.png) [@ilana8](https://community.questdb.com/u/ilana8)\ **Post date:** [August 2, 2024, 6:23pm UTC](https://community.questdb.com/t/error-in-restore-snapshot/141/1 "2024-08-02T18:23:05Z")
I am using the instructions for [Backup and restore | QuestDB](https://questdb.io/docs/operations/backup/) to migrate a database to a new machine. I am getting an error upon restarting the service; it starts going through the restore process, seems to do ok with a few of my data tables, but fails at the telemetry\_wal table. I’m not finding much guidance on how to debug this. I’ve tried re-creating the snapshot information with `snapshot prepare` (original DB has not changed) and copying that into the new location, but that didn’t have any effect. Suggestions on how to proceed? > 2024-08-02T18:15:48.156951Z I i.q.c.DatabaseSnapshotAgentImpl rebuilding symbol files [table=/home/user/.questdb/db/telemetry\_config, column=version, count=2] > 2024-08-02T18:15:48.157281Z I i.q.c.DatabaseSnapshotAgentImpl rebuilding symbol files [table=/home/user/.questdb/db/telemetry\_config, column=os, count=1] > 2024-08-02T18:15:48.157669Z I i.q.c.DatabaseSnapshotAgentImpl rebuilding symbol files [table=/home/user/.questdb/db/telemetry\_config, column=package, count=1] > 2024-08-02T18:15:48.158035Z I i.q.c.DatabaseSnapshotAgentImpl recovered \_meta file [src=/home/user/.questdb/snapshot/db/sys.telemetry\_wal/\_meta, dst=/home/user/.questdb/db/sys.telemetry\_wal/\_meta] > 2024-08-02T18:15:48.158135Z I i.q.c.DatabaseSnapshotAgentImpl recovered \_txn file [src=/home/user/.questdb/snapshot/db/sys.telemetry\_wal/\_txn, dst=/home/user/.questdb/db/sys.telemetry\_wal/\_txn] > 2024-08-02T18:15:48.158227Z I i.q.c.DatabaseSnapshotAgentImpl recovered \_cv file [src=/home/user/.questdb/snapshot/db/sys.telemetry\_wal/\_cv, dst=/home/user/.questdb/db/sys.telemetry\_wal/\_cv] > 2024-08-02T18:15:48.159431Z I i.q.c.p.WriterPool closed > 2024-08-02T18:15:48.159472Z I i.q.c.p.ReaderPool closed > 2024-08-02T18:15:48.159500Z I i.q.c.p.SequencerMetadataPool closed > 2024-08-02T18:15:48.159545Z I i.q.c.p.TableMetadataPool closed > 2024-08-02T18:15:48.159574Z I i.q.c.p.WalWriterPool closed > java.lang.AssertionError > at io.questdb@8.1.0/io.questdb.std.LongList.setQuick(LongList.java:420) > at io.questdb@8.1.0/io.questdb.cairo.TxReader.unsafeLoadPartitions(TxReader.java:543) > at io.questdb@8.1.0/io.questdb.cairo.TxReader.unsafeLoadAll(TxReader.java:423) > at io.questdb@8.1.0/io.questdb.cairo.TxWriter.unsafeLoadAll(TxWriter.java:450) > at io.questdb@8.1.0/io.questdb.cairo.TxWriter.ofRW(TxWriter.java:241) > at io.questdb@8.1.0/io.questdb.cairo.DatabaseSnapshotAgentImpl.rebuildTableFiles(DatabaseSnapshotAgentImpl.java:179) > at io.questdb@8.1.0/io.questdb.cairo.DatabaseSnapshotAgentImpl.lambda$recoverSnapshot$0(DatabaseSnapshotAgentImpl.java:565) > at io.questdb@8.1.0/io.questdb.std.FilesFacadeImpl.iterateDir(FilesFacadeImpl.java:285) > at io.questdb@8.1.0/io.questdb.cairo.DatabaseSnapshotAgentImpl.recoverSnapshot(DatabaseSnapshotAgentImpl.java:554) > at io.questdb@8.1.0/io.questdb.cairo.CairoEngine.(CairoEngine.java:137) > at io.questdb@8.1.0/io.questdb.Bootstrap.newCairoEngine(Bootstrap.java:366) > at io.questdb@8.1.0/io.questdb.ServerMain.(ServerMain.java:85) > at io.questdb@8.1.0/io.questdb.ServerMain.(ServerMain.java:79) > at io.questdb@8.1.0/io.questdb.ServerMain.main(ServerMain.java:172) ---
**Author:** ![goodroot](https://yyz2.discourse-cdn.com/flex004/user_avatar/community.questdb.com/goodroot/32/16_2.png) [@goodroot](https://community.questdb.com/u/goodroot)\ **Post date:** [August 2, 2024, 6:29pm UTC](https://community.questdb.com/t/error-in-restore-snapshot/141/2 "2024-08-02T18:29:42Z")
Hi @ilana8 – Nothing jumps out immediately. As other folks on the team see it, something may. For now, I’d like to point to this reference document that we have in addition to the SNAPSHOT guide: > **[SNAPSHOT keyword | QuestDB](https://questdb.io/docs/reference/sql/snapshot/)** > > SNAPSHOT SQL keyword reference documentation. Perhaps the reference method and the additional context might lead to a revelation. We’ll return if anything jumps out - please update us with new findings. ---
**Author:** ![ilana8](https://avatars.discourse-cdn.com/v4/letter/i/848f3c/32.png) [@ilana8](https://community.questdb.com/u/ilana8)\ **Post date:** [August 2, 2024, 7:29pm UTC](https://community.questdb.com/t/error-in-restore-snapshot/141/3 "2024-08-02T19:29:11Z")
I removed the `sys.telemetry_wal` directory out of `snapshots/db`, since that seemed to be causing the problem. Then on the next restart, it recovered and rebuilt all the tables, and i see that it does > 2024-08-02T19:07:19.040981Z I i.q.g.e.QueryProgress exe [id=3, sql=`CREATE TABLE IF NOT EXISTS "sys.telemetry_wal" (created timestamp, event short, tableId int, walId int, seqTxn long, rowCount long,physicalRowCount long,latency float) timestamp(created) partition by MONTH BYPASS WAL`, principal=admin, cache=false, jit=false] along the way as well. DB is up and seems to be fine. I don’t know what sys.telemetry\_wal does, but hopefully it won’t be an issue later. ---
**Author:** ![nwoolmer](https://yyz2.discourse-cdn.com/flex004/user_avatar/community.questdb.com/nwoolmer/32/24_2.png) [@nwoolmer](https://community.questdb.com/u/nwoolmer)\ **Post date:** [August 5, 2024, 8:44am UTC](https://community.questdb.com/t/error-in-restore-snapshot/141/4 "2024-08-05T08:44:12Z")
The telemetry table records basic information about what the database is doing. This is very coarse information, and should not interfere with normal processing. This could be an old bug, or something new introduced in our recent `SNAPSHOT` updates. We should be able to resolve this soon, possibly in the next version. Glad you have a resolution for now!