Receiving ORA-600 [Pitl1] When Altering A Table

Symptoms

When attempting to update table the following error occurs:

ERROR
ORA-00600: internal error code, arguments: [PITL1]

You may see some or all of the following function codes in the 'stack trace' portion of the associated trace file:
kdtgrs <- kdtInsRow <- kdumrp <- kduurp <- kdusru <- kauupd <- updrow <- qerupRowProcedure <- 050 <- qerupFetch <- updaul <- updThreePhaseExe <- updexe <- opiexe <- opipls <- opiodr <- rpidrus <- skgmstack <- rpidru <- rpiswu2 <- rpidrv <- psddr0 <- psdnal <- pevm_EXECC <- pfrinstr_EXECC
<- pfrrun_no_tool <- pfrrun <- plsql_run <- peicnt <- kkxexe <- opiexe <- kpoal8 <- opiodr <- ttcpip <- opitsk <- opiino <- opiodr <- opidrv <- sou2o <- opimai_real <- main <- start

Running the sql:

analyze table ... validate structure;

will reveal "PITL Invariant Violation" corruption.

Cause