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SQLite error code

SQLITE_READONLY_CANTLOCK

SQLITE_READONLY_CANTLOCK is SQLite result code 520, an extended code of SQLITE_READONLY.

Result code520
NameSQLITE_READONLY_CANTLOCK
Primary codeSQLITE_READONLY

What it means

The SQLITE_READONLY_CANTLOCK error code is an extended error code for SQLITE_READONLY. The SQLITE_READONLY_CANTLOCK error code indicates that SQLite is unable to obtain a read lock on a WAL mode database because the shared-memory file associated with that database is read-only.

Source: SQLite Result and Error Codes